The Conjugate Acid For The Weak Base Ch3ch2nh2

0 × 10 − 14. •These conjugate bases are weak bases. Salts of SA/WB are acidic. Weak acids have varying strengths dependent on their pKas, so you have acids that are weak acids, but strong relative to other weaker acids, and vice versa. What is the pH of the mixture? The HCL should react with the basic component of the buffer - changing it to its conjugate acid: We need to find out the NEW concentrations of all the species in the buffer solution. Hydrogen ions, which maintain membrane integrity and the speed of enzymatic reactions, must be concentrated within a narrow range if the body is to function normally. Calculate the pH of the solution after these volumes of the titrant have been added. 040 M KOH (aq); (d) household ammonia in which the [OH¯]= 3 x 10 -3 M; (e) 6. The conjugate acid of the deprotonated amine is the neutral amine (pKa=40), while the conjugate acid of the neutral amine is the ammonium (CH 3 NH 3 +, pKa=10. It is the substance that gets created once a acid looses a [H+] proton ; This is all known as a conjugate acid-base pair. A conjugate acid is a substance that has one more proton in its structure than its corresponding conjugate base. E Water competes with the weak acid to react with the base, raising the concentration of hydroxide ions. Acid-base buffers confer resistance to a change in the pH of a solution when hydrogen ions (protons) or hydroxide ions are added or removed. 7 x 10 −10 (from the relationship K a × K b = 10 −14), which certainly does not correspond to a strong base. For example, Here, is the acid, is the base, is the conjugate acid and is the conjugate base. The conjugate acid-base pairs for this reaction are NH 4 + /NH 3 and H 2 O/OH -. Weak Acid/Weak Base (definitions and eg) Only partially dissociates (ionises) in solution/water (only a small amount of H+ is formed) eg CH3COOH (all carboxylic acids); NH3, CH3CH2NH2 (amines and amides). But keep in mind that a proton carries a 1+ charge, so make sure that you. Another way to think about it,. $\ce{CH3CH2NH3Cl}$ is acidic because it is formed from a strong acid ($\ce{HCl}$) and a weak base ($\ce{CH3CH2NH2}$). The conjugate of a weak acid is often a weak base and vice. Thus the product of the acid constant for a weak acid and the base constant for the conjugate base must be K w, and the sum of pK a and pK b for a conjugate acid-base pair is 14. C The reaction produces a strong conjugate base and a weak conjugate acid. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory. It's something that contains both a weak acid, which generically we write as HA, and it also contains in equilibrium the conjugate base of our acid, so A minus. 300ml pure water- Calculate the initial and final pH B. Notice that the two solutes, H2PO4 - and HPO. For example, take the following dissocia. Some common conjugate acid–base pairs are shown in Figure 2. It can be used to determine pH. When a weak acid reacts with a weak base, the equivalence point solution will be basic if the base is stronger and acidic if the acid is stronger. Weak bases: Compounds that contain electron rich N, Amines such as CH3CH2NH2 Strong bases: Soluble hydroxides. 310 M in KCHO2, Calculate the initial pH and the final pH after adding 0. 8 x 10-5) and 0. for each of the following solutions calculate the initial pH and the final pH after adding 0. Strong acids will neutralize strong bases of equal concentrations in. solution does not have a buffer, the addition of a strong acid or strong base would dramatically change the pH since there will be no conjugate weak acid or weak base to consume the added ions. The conjugate base of strong acids are very weak bases. conjugate acid-base pair: in prototonic solvents (for example, H 2 O, NH 3 , acetic acid), two molecular species differing only in the presence or absence of a hydrogen ion (for example, carbonic acid/bicarbonate ion or ammonium ion/ammonia); the basis of buffer action. Hence, for NH 2-the conjugate acid would be NH 3 (the positive charge of H + and the negative charge of NH 2- cancel each other out). A buffer is a combination of a weak acid and its salt or a weak base and its salt. acid base conjugate base conjugate acid conjugate acid: the species produced when a base accepts a hydrogen ion from an acid conjugate base: species that results when an acid donate a hydrogen ion to a base conjugate acid-base pair:consists of two substances related to each other by donating and accepting of a single hydrogen ion Conjugate Base Pairs Video. after 30 mL of NaOH. NH3 + H2O NH4+ + OH- base acid conjugate conjugate acid base. Weak acids and weak bases. 0 M HCl to 1. Calculate the pH of a 0. Acetic acid has a proton that it can transfer, so it is an acid, while ammonia can accept a proton, so it is a base. asked by kim on April 30, 2015; chem. The conjugate acid of a weak base will be a weak acid. 12 M Chapter 7 Acids and Bases 7. The conjugate acid of the weak base makes pH < 7. The pKa for acetic acid is 4. 76 x 10 -4phenol 1. 77 | C3H50(COOH)(COO-)2 dihydrogen citrate ion hydrogen citrate ion 9. And vice versa, weak acids have strong conjugate bases and weak bases have strong conjugate acids. 90 x 10-2 [H 2 SO 3] = SO 2 (aq) + H2 O HSO. The value of pKb for the base ethylamine (CH3CH2NH2) is 3. HA(aq) + H 2 O(l. 13 propanoate ion 5. Acid-base reactions don't have to occur in water. NH 4 OH will dissociate less in a solution containing NH 4 Cl salt. Less than 40 years later, in 1923, Bronsted, Lowry and Lewis wanted to expand the concepts of acids and bases so that a wider area of chemistry can be. Relate the strength of a weak acid to the strength of its conjugate base. Figure \(\PageIndex{1}\). A weak acid (e. Which of these is not a true statement? A) All Lewis bases are also Bronsted -Lowry bases. 3 * 10-4 at 25degree C, what is the value of Ka for CH3CH2NH3 at 25 C? How To Relate K_a and K_b for Conjugate Acid-Base Pairs. In each case write the formula of its conjugate acid, and indicate whether the conjugate acid is a strong acid, a weak acid, or a species with negligible acidity: (a) CH 3 COO –, (b)HCO 3 –, (c) O 2–, (d) Cl –, (e) NH 3. Say if I have a base let's say I have Ammonia or NH3 and that's on water so we use our double yield sign. which is the strongest acid? a) CH3C=CH b) CH3OH c) CH3CH2F d) CH3CH2CH3 e) CH3NH2 2. Evolution of the Acid-Base Concept. Mencken Conjugate acid/base pairs 1. Example: Acid is HX and conjugate base is X^-. The equilibrium favors towards the weaker acid and weaker base in an acid-base reaction. For example, ammonia and ammonium nitrate. Another thing to note is that CH3CH2NH3 + and CH3CH2NH2 are a acid/conjugate base pair which means that the above equation can be used. The weaker the acid is, the stronger its conjugate base. When a base donates its lone pair to an acid, for example, a base accepts a proton. Thus the product of the acid constant for a weak acid and the base constant for the conjugate base must be K w, and the sum of pK a and pK b for a conjugate acid-base pair is 14. Consider the following compounds: (4) CH3CH2NH2 CH3CH2OH CH3CH2CH3 CH3COOH a. Therefore, we can conclude that in the given chemical reaction and is the base-conjugate acid pair. This case occurs when water is not a solvent because water does not conveniently extract H + ion from the conjugate base. The converse is also true; if an acid's conjugate base is weak, then the acid must be strong. Hence, the conjugate base of propanoic acid, is,. Since HCl is considered to be infinitely strong, Cl- is infinitely weak as a base. Weak acids and weak bases. The other NH 3 molecule acts as an acid and donates a proton to form NH 2. Br- is a very weak base; HBr is a strong acid. When this acid donates an H + ion to water. Below is a graph of a weak acid titration, which is also a graph of the Henderson-Hasselbalch equation, showing how pH changes as acid or base is added. Assuming you are asking about the base I-, the conjugate acid is HI, hydroiodic acid. Thus, HA and A − are conjugate acid-base pair. Start studying Conjugate acid &base. Acid is HCl, conjugate base is Cl^-. Two curved arrows are needed. In 1884, Arrhenius noticed that all acids have \(\ce{H+}\) ions and bases have \(\ce{OH-}\) ions. Therefore F(-) is a strong base. 76 x 10 -4phenol 1. The balanced conjugate acid-base pair reaction will be, In this reaction, is a weak acid which donate a proton to which is a weak base to form as a conjugate base and as a conjugate acid. Examples of how to use “conjugate base” in a sentence from the Cambridge Dictionary Labs. unstable) 4. (A) Acid : Strong Acid vs Weak Acid Monoprotic Acid / Diprotic Acid / Triprotic Acid (B) Base: Strong Base vs Weak Base Take note of concentration of acid / bases (For dilute solutions, we need to take into consideration of [H+] / [OH-] from auto-ionization from water)Step 2: Use the appropriate equations for the respective species. 8 x 10 -5 ) with 0. The value of K a is used to calculate the pH of weak acids. 9 10-10 (pK a = 9. a) HCO 3-The ionization reaction is as follows. The higher the pka, the weaker the acid; thus the stronger its conjugate base. Which labeled equation shows the reaction of CH3CH2NH2 with H2O and correctly labels the conjugate acid and the conjugate base for the reaction? an you write the balance equation with correct charges?. Consider an acid, HA, in water. Give the conjugate acid of a base. This goes for the base too; the base corresponds to the conjugate acid on the product side of the equation. * A base. Treat the conjugate acid of a base as an acid in numerical calculations. For a weak acid (HA) in water: HA + H2O H3O+ + A-Ka HA HA = [][]+− [] [] [] [] H HA a A + − =K pH p A a HA =+ − Klog [] [] For a conjugate acid (BH +) of a weak base(B) in water: BH+ + H2O H3O+ + B Ka + HB BH = [][]+ [] [] [] [] H BH a B + + =K pH p B a BH+ =+Klog [] [] NOTICE! You can NOT look up the Ka of BH+. For example, a buffer could be prepared by mixing 1. 0 x 10-14 and ka and kb are the acid and base constants, respectively. In your explanation, use more than just the pKa values. Asked May 8, 2020 Conjugate pair consist a group of acid - base pair. 25 | C5H5N pyridinium ion C5H5NH+ pyridine carbonic acid. You find pka by taking -log(ka), but since you're just measuring them against each other, you really dont need the numbers. c) ClO 4 – or ClO 2 – HClO 2 is weaker acid than HClO 4. Acid strength is solvent-dependent. If you take away the proton (or add it), you get the other formula. Answer to: Identify the conjugate acid-base pairs from the following reactions: A. NH 3 is the base. The conjugate acid of any species, is that species plus a proton; so it's H2PO− 4. Every acid-base reaction contains two conjugate acid-base pairs because an H is transferred in both the forward and reverse directions. A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed by the reception of a proton (H +) by a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. 100M HC 2 H 3 O 2 (Ka=1. 170 M}$ in $\ce{CH3CH2NH2}$ and $\pu{0. Since hydroiodic acid is a strong acid, it can be concluded that iodide (I-) is a weak conjugate base. q In order to use this method, the compounds (amine and carboxylic acid, as well as the product amide) must be thermally stable. The buffer components HA and A- are related to each other by means of the following chemical reaction that describes the behavior of a weak acid in water (Equation 1). These are formed wither by a weak base and its conjugate acid or a weak acid and its conjugate base. 8 x 10-1 H 2 C 2 O 4 (oxalic acid) HC 2 O 4 - 5. Every Brønsted-Lowry acid-base reaction can be labeled with two conjugate acid-base pairs. Comparing the other two to ammonia, you will see that methylamine is a stronger. An acid–base reaction is a chemical reaction that occurs between an acid and a base. Weak bases partially dissociate in solution. A buffer will be effective as long as the [base]:[acid] ratio remains between 0. Get 1:1 help now from expert Chemistry tutors. CH3COOH is also a weak acid (not as weak as ethanol). 25 acetic acid acetate ion C3H50(COOH)2COO- | 4. 010 C End The strong base is converting the weak acid into a weak base (its conjugate base). 18 CH3CH2COOH 4. b) a weak base in the presence of a salt that contain the conjugate acid What is the pH of a solution that contains 0. These relationships have been represented by. weak electrolytes. The thing to remember about conjugate acids is that they are the chemical species that is formed when a Bronsted-Lowry base accepts one proton, "H"^(+). The conjugate acid ofCH3CH2NH2will beCH3CH2NH3+ CH3C view the full answer. In this experiment we will be dealing with the former combination (weak acid/conjugate base). Salts of WA/SB are basic. Answer to: Identify the conjugate acid-base pairs from the following reactions: A. Titrations of Weak Bases with Strong Acids 1. This is what happens when a weak acid and a strong base are mixed in exact proportions. acid base Acid-Base Equilibrium Conjugate Acid/Base Pairs •HA(aq) + H2O(l) Æ H3O+(aq) + A-(aq) conj conj acid 1 base 2 acid 2 base 1 •conjugate acid: formed when the proton is transferred to the base. Although it's approximate, it will be close enough (accurate to 2 or 3 significant figures) to use this MOST of the time. Identify the major species in solution before, at and after equivalence point 2. A strong acid yields a weak conjugate base (A –), so a strong acid is also described as an acid whose conjugate base is a much weaker base than water. The sample and titrant are essentially creating a buffer solution that contains unreacted weak acid (HA) and newly formed conjugate base (A-). However, the conjugate acid of weak base with be a weak acid, and its presence will mean that a pH less than 7 will be observed, giving an acidic solution. According to the Brønsted-Lowry acid/base theory, the acid should protonate the water to form hydronium and the conjugate base, A-. Strong acids and pH. Value of K w for water is 1. Hence, for NH 2-the conjugate acid would be NH 3 (the positive charge of H + and the negative charge of NH 2- cancel each other out). Are both mass and charge conserved here? By the same procedure, if I remove H^+ from any species, I get the conjugate base. ( Crowe and Bradshaw 2010)Many life forms thrives only in a relatively small pH range so they utilize a buffer solution to. Identify the conjugate acid-base pairs in the reaction. What is the pH of the mixture? The HCL should react with the basic component of the buffer - changing it to its conjugate acid: We need to find out the NEW concentrations of all the species in the buffer solution. Therefore you may consider the acidity of the listed organic compound: CH3COOH is the strongest acid in the list, therefoee CH3COO- is the weakiest conjugate base. Which of the following is a conjugate pair? OH and H30* CH3CH2NH2 and CH3CH3NH3* Question. stronger, weaker a titration of a strong acid with a strong base will always have a pH of __ 7 a weak acid titration equivalence point will be basic a weak base titration equivalence point will be acidic. Comparing the other two to ammonia, you will see that methylamine is a stronger. Thus, HA and A − are conjugate acid-base pair. 13 propanoate ion 5. Usmle step 3 Question and Answers 2020 You are called emergently to the medical floor where a 66-year-old man was found to be minimally responsive. And the conjugate acid of any base is the original base PLUS a proton. For example, OH – is the conjugate base of H 2 O, and X – is the conjugate base of HX. All buffers contain a mixture of either a weak acid (HA) and its conjugate base (A-), or a weak base and its conjugate acid. 1 from the textbook, we are asked to write the formula of the conjugate base of HCO3- (book answer: H2CO3) and the conjugate acid of HCO3- (book answer: CO3^2-). 6 g = 26 g using sig fig. b) The sodium hydroxide will react completely with the acetic acid to form water and sodium acetate. 50 M solution of the base ethylamine, CH3CH2NH2. Water is acting like an acid in this case. Given: Value of p K a for conjugate acid of given weak base (CH 3) 3 N is 9. The reason that acetic acid dissociates into acetone rather than water is. HA(aq) + H 2 O(l. 0 x 10-14 and ka and kb are the acid and base constants, respectively. So the volume of "a" would just be whatever volume allowed for an equal number of moles of weak acid and strong base. CH3CH2OH + NaOH 2. 00 M HCl to the buffer solution. LeChateliers principle: A system in equilibrium will move to the right or to the left to accommodate any stress. Consider the following compounds: (4) CH3CH2NH2 CH3CH2OH CH3CH2CH3 CH3COOH a. 25 acetic acid acetate ion C3H50(COOH)2COO- | 4. What is the conjugate base of CH3CH2NH3+ ? Answer Save. 77 | C3H50(COOH)(COO-)2 dihydrogen citrate ion hydrogen citrate ion 9. This is due to the production of a conjugate acid during the titration; it will react with water to produce hydronium (H 3 O +) ions. acid + salt of conjugate base. Draw the conjugate base of CH3CH2NH2. 3 base NH 4 + conjugate acid OH- conjugate base Brønsted-Lowry Acids & Bases Identify each species in the following equation as etiher the Brønsted-Lowry acid, the Brønsted-Lowry base, the conjugate acid, or the conjugate base. In response to the additional. lithium hydroxide strong base c. “Comparable amounts” generally means that the concentrations are within a factor of 10 of each other. A conjugate acid, within the Brønsted-Lowry acid-base theory, is a chemical compound formed by the reception of a proton (H +) by a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. Acids can be strong or weak. H 2S: remove one H + to make HS–. Which of these is not a true statement? A) All Lewis bases are also Bronsted -Lowry bases. Our definition of a weak acid or base is 1 > K > K w. Relationship between Ka and Kb for conjugate acid-base pairs Recall that there is an inverse relationship between the strength ofan acid and the strength of its. At equilibrium, the weaker acid and the weaker base are the major species found in the reaction mixture. 1 M solution of NaOH, the OH − is 0. Acid is HCl, conjugate base is Cl^-. 6 g/mol, requiring 25. Strong acid produces weak conjugate base, strong base produces weak conjugate acid. A weak acid will have a strong conjugate base and a strong acid will have a weak conjugate base. Are both mass and charge conserved here? By the same procedure, if I remove H^+ from any species, I get the conjugate base. Br- is a very weak base; HBr is a strong acid. O2-The answer is easy if you understand conjugate base/acid theory. Question: Given that Kb for CH3CH2NH2 is 6. That species is. base of HCO3- Post by ttay190190 » Sat Dec 07, 2013 8:24 pm In parts (c) and (d) of problem 11. Then, add –1 to the charge of the acid to give the charge on the conjugate base. You do not necessarily have to convert pKb to pKa and back to Ka (but you could of course, since you know that it would have a pKa of 12, which means it has a lower Ka, and thus would be a weak. Equation \(\ref{6}\) or \(\ref{10}\) enables us to calculate the base constant of a conjugate base from the acid constant of the acid, and vice versa. 05 M tris / 0. 46 x 10-5 M Concentration (M) HClO(aq) + H2O(l) H3O+(aq) + ClO -(aq) Initial 0. In both cases identify the conjugate acid– base pairs. Explain why the conjugate acid of the weak base NH3 is a weak acid. 82 CH3CH2CH2COO butanoate ion 9. c) ClO 4 – or ClO 2 – HClO 2 is weaker acid than HClO 4. chemistnate. Acid K abutyric acid 1. This is considered the acid and since OH- is ready to accept a proton this is the conjugate base It is very similar for bases and conjugate acids, since NH 3 and NH4+ differ by a single proton and single charge. Rank the following sets of compounds in order of decreasing acidity. TABLE OF CONJUGATE ACID-BASE PAIRS Acid Base K a (25 oC) HClO 4 ClO 4 - H 2 SO 4 HSO 4 - HCl Cl- HNO 3 NO 3 - H 3 O + H 2 O H 2 CrO 4 HCrO 4 - 1. H 2SO 4 (aq) + HPO 4 2- (aq) ! HSO 4 - (aq) + H 2PO 4. So, the conjugate base of acetic acid is a molecule of acetic acid missing an electron, or a hydrogen, and has a negative charge. Remember conjugate pairs differ by only one proton. Thus NH 3 is called the conjugate base of NH 4 +, and NH 4 + is the conjugate acid of NH 3. The conjugate acid ofCH3CH2NH2will. 0 M sodium acetate, NaCH 3­ COO. The presence of resonance stabilizes the conjugate base, making it a weaker base. CH 3 COOH is a much weaker acid, so it will have a stronger conjugate base. For example, acetic acid and sodium acetate. Acid-Base Practice Problems A. Tags: Question 13. 6 g/mol, requiring 25. This problem has been solved! See the answer. Recall that a strong acid is 100% dissociated in solution (Chapter 4). 25 for the acetate ion and comparing to the pKb values, it is not that strong a base. On arrival, chest compressions are being performed and 2 operators are mask ventilating the patient. 6) When a base is added to water, there is a Bronsted-Lowry acid base reaction where the base behave as a base and water acts as the acid. Get 1:1 help now from expert Chemistry tutors. 9 10-10 (pK a = 9. HF is a weaker acid than HCl. In the reverse reaction, NH 4 + donates a proton. The weaker the acid is, the stronger its conjugate base. Conjugate Acids and Bases HCN(aq) + H 2O H Conjugate Acids and Bases HCN is a rather weak acid, K a = 4. Buffers are most effective when the [acid] and [base] are large. 12 M - x = 0. We can see a much bigger effect with substituted carboxylic acids. The conjugate base of CH3CH2NH2: The concept of conjugate acid and conjugate base came from the Bronsted-Lowry theorem. Equation \(\ref{6}\) or \(\ref{10}\) enables us to calculate the base constant of a conjugate base from the acid constant of the acid, and vice versa. Water is acting like an acid in this case. Brönsted acids bases examples. A buffer will be effective as long as the [base]:[acid] ratio remains between 0. 0 x 10-14 /6. If you titrate acetic acid (CH3COOH) with sodium hydroxide (NaOH) the resulting products are the acetate ion (CH3COO-), the sodium ion, and water (see figure 1). a is the base of methanol, and the bases of alcohols are very reactive (i. Conjugate bases and acids occur with weak acids, such as acetic acid. 02 x 10 -10A. Acid K abutyric acid 1. 0 x 10-14 and ka and kb are the acid and base constants, respectively. The conjugate base of bicarbonate, HCO 3- is carbonate, CO3 2-. 25 | C5H5N pyridinium ion C5H5NH+ pyridine carbonic acid. C) All Bronsted -Lowry acids contain hydrogen. Start studying Chem 122 test 4. A buffer will be effective as long as the [base]:[acid] ratio remains between 0. 23 butanoic acid CH3CH2CH2COOH 4. 3 * 10-4 at 25degree C, what is the value of Ka for CH3CH2NH3 at 25 C? How To Relate K_a and K_b for Conjugate Acid-Base Pairs. and conjugate acid is methane. According to the Bronsted-Lowry theory, an acid is a proton donor and a base is a proton acceptor. A hint: the conjugate base of a strong acid is usually weak, and vice verse (ie one of the conjugate pairs will be strong and the other will be weak; the strong one can be either base or acid). Since HCl is a strong acid, Cl-is a weak base. H2SO4 + NH3 HSO4- + +NH4 acid. If BOH is a very strong base, B + will be a very weak acid and will not affect the pH of a solution. Brönsted acids bases examples. The equilibrium favors towards the weaker acid and weaker base in an acid-base reaction. NH 2 is the conjugate base of the NH 3 acid. Thus, only in the rare circumstance when the molar concentrations of the conjugate acid and conjugate base in a solution are equal, the pH = pK a. Acid/Base Properties of Salts Hydrolysis of Salts Salts of SA/SB are neutral. Table \(\PageIndex{1}\) gives a list of some of the more important conjugate acid-base. Explain why the conjugate acid of the weak base NH3 is a weak acid. Some compounds can act as both acids & bases. Acid Base Conjugate Conjugate. 182 Take 100. NH 3 is the base. Acids, Bases, and Properties - HW PSI AP Chemistry Name_____ Earlier definitions, conjugate acid/base, strong and weak acids and bases, Ka and Kb relation to the strength of the acid or base, pH, pOH, [OH-], [H+] , percent ionization of weak acid /base 1) According to the Arrhenius concept, an acid is a substance that _____. Suggested Problems for Acid/Base Reactions Instructions: Show products, identify the acid, base, conjugate acid, conjugate base and indicate to which side the equilibrium will lie. 12 M - x = 0. Step 7) Once even more OH-is added, the pH of the solution continues to rise. Calculate the pH of a 0. Its conjugate base is a weak base. H 2O and NO3-compete for H+ ions. The pK a value is used to choose a buffer when needed. at the midpoint d. Conjugate acid-base pair vary by a H+ion. pick and chose which two you want to memorize. A weak acid will react with a strong base to form a basic (pH > 7) solution. Conjugate acids- Bases are differed by a proton. Conjugate acids and bases are part of the Bronsted-Lowry theory of acids and bases. In the reverse reaction, an ammonium ion acts as an acid by donating a proton to a hydroxide ion, and the hydroxide ion acts as a base. So when the weak acid (phosphoric acid) loses a hydrogen ion, it will form on the other side the weak conjugate base ie. 30] The most commonly encountered weak base is ammonia: [16. •In every acid-base reaction, the position of the equilibrium favors the transfer of a proton from the stronger acid to the. 2) (45 points) This problem deals with a 0. q The carboxylic acid is a weak acid, but at higher temperatures (150 – 200 oC), it can act as an acid catalyst. Mencken Conjugate acid/base pairs 1. The balanced conjugate acid-base pair reaction will be, In this reaction, is a weak acid which donate a proton to which is a weak base to form as a conjugate base and as a conjugate acid. A weak acid and its conjugate base can be in a solution with neutralizing each other, and same goes for a weak base and its conjugate acid. 12 ---- ----- ----- Change -x ---- +x +x Equilibrium 0. 25 | C5H5N pyridinium ion C5H5NH+ pyridine carbonic acid. lithium hydroxide strong base c. Since HCl is a strong acid, Cl-is a weak base. If BOH is a very strong base, B + will be a very weak acid and will not affect the pH of a solution. Electron-withdrawing groups stabilize the conjugate base while electron-donating groups destabilize the conjugate base. Methyllithium reacts with water to yield conjugate base lithium hydroxide that is LiOH. Another example is CH3COOH or acetic acid. Arrange the conjugate bases of the acids given in part (a) in order of increasing basicity and explain your reasoning. 0 x 10-14 and ka and kb are the acid and base constants, respectively. Every time a Brnsted acid acts as an H +-ion donor, it forms a conjugate base. It can be used to determine pH. 0 mL of a buffer solution that is 0. ii: Define the term weak base according to the Brønsted–Lowry theory. Conjugate bases or conjugate acids are simply a proton added or removed to the. Similarly, when a base gains a proton, then it forms a conjugate acid. Good! This relationship is also seen with bases and their conjugate acids. Which of the following is a conjugate pair? OH and H30* CH3CH2NH2 and CH3CH3NH3* Question. Acid is HCl, conjugate base is Cl^-. Therefore you may consider the acidity of the listed organic compound: CH3COOH is the strongest acid in the list, therefoee CH3COO- is the weakiest conjugate base. Bases that are weak have relatively strong conjugate acids. Therefore, it is very important to be able to identify acid and conjugate base pairs. Usmle step 3 Question and Answers 2020 You are called emergently to the medical floor where a 66-year-old man was found to be minimally responsive. Weak bases: Compounds that contain electron rich N, Amines such as CH3CH2NH2 Strong bases: Soluble hydroxides. The _____ the weak acid, the _____ the conjugate base. at the midpoint d. For "d" I'm now thinking that the volume beyond the equivalence point because that would mean that the predominant species is the conjugate base. In acid-base reactions, the acid donates a proton and the species that is left is its conjugate base. phenol, butyric acid, hydrofluoric acidD. Because bases ACCEPT protons, so therefore NH2 is more willing to accept a proton than NH3+ 0 0 0. Conjugate acids- Bases are differed by a proton. In 1884, Arrhenius noticed that all acids have \(\ce{H+}\) ions and bases have \(\ce{OH-}\) ions. The conjugate base of a weak acid is a weak base, while the conjugate acid of a weak base is a weak acid. Example: Acid is HX and conjugate base is X^-. Relate the strength of a weak acid to the strength of its conjugate base. i know gaseous co2 dissolves in solution for h2co3, carbonic acid. According to this theorem, when a species donates a proton. The name of the base is chloride ion. For example, a buffer could be prepared by mixing 1. Expert Answer. And the conjugate acid of any base is the original base PLUS a proton. Brønsted Acids and Bases in Nonaqueous Solutions. The weak bases tends to neutralize any extra acid added to the buffer, and the weak acid tends to neutralize any extra based added. C) All Bronsted -Lowry acids contain hydrogen. The conjugate acid is created by accepting (adding) a proton (H +) donated by the conjugate base. The other conjugate pair is: H 2 O and H 3 O + Water is the base, since it is minus a proton compared to H 3 O +, which is the conjugate acid to water. 51 x 10 -5hydrofluoric acid 6. Acid-Base Practice Problems A. An acid and a base which differ only by the presence or absence of a proton are called a conjugate acid-base pair. Asked May 8, 2020 Conjugate pair consist a group of acid - base pair. O2-The answer is easy if you understand conjugate base/acid theory. Two curved arrows are needed. Answer to: Identify the conjugate acid-base pairs from the following reactions: A. (For a neutral base, B:(aq), the conjugate acid will be cationic, HB+(aq). So first of all, you can neglect that the acid CH3COOH will dissociate to CH3COO-, as by the above argument, it only dissociates to a very little extent. (A) Acid : Strong Acid vs Weak Acid Monoprotic Acid / Diprotic Acid / Triprotic Acid (B) Base: Strong Base vs Weak Base Take note of concentration of acid / bases (For dilute solutions, we need to take into consideration of [H+] / [OH-] from auto-ionization from water)Step 2: Use the appropriate equations for the respective species. base • By convention, the acids considered "strong" have Ka > 1 while "weak" acids have Ka < 1. This is at equilibrium, but when you add conjugate base (A-), you are perturbing the equilibrium. Another example is CH3COOH or acetic acid. Therefore, a molecule to behave as an acid should encounter a. But the conjugate base could still be a weak base. Acid is HCl, conjugate base is Cl^-. A weak acid is a proton donor that when put in water will only partially dissociate. E Water competes with the weak acid to react with the base, raising the concentration of hydroxide ions. conjugate acid: the species created when a base accepts a proton In chemistry, a base is a substance that can accept hydrogen ions (protons) or, more generally, donate a pair of valence electrons. 00 M HCl to the buffer solution. The value of pKb for the base ethylamine (CH3CH2NH2) is 3. So, the conjugate base of acetic acid is a molecule of acetic acid missing an electron, or a hydrogen, and has a negative charge. Given: Value of p K a for conjugate acid of given weak base (CH 3) 3 N is 9. 2) What is the strongest base in the following reaction? HNO3(aq) + H. Write the reaction that occurs, and identify the conjugate acid– base pairs. (HB) in their conjugate acid form, or deprotonated (B: ) in their basic form. The sample and titrant are essentially creating a buffer solution that contains unreacted weak acid (HA) and newly formed conjugate base (A-). 46 x 10-5 M Concentration (M) HClO(aq) + H2O(l) H3O+(aq) + ClO -(aq) Initial 0. send the reaction completely to the right. 010M acetic acid solution. 8 x 10 -5 ) with 0. hydrofluoric acid weak acid Exercise 5. The conjugate acid of a base is formed by the protonation (reception of a hydrogen cation) of the acid. It dissociates into acetone ion which is a strong base. Get 1:1 help now from expert Chemistry tutors. •conjugate base: everything that remains of the acid molecule after a proton is lost. Note: basicity for these conjugate base is the reverse of the acidity trend For every Acid, there is a conjugate base To draw a conjugate base, just remove a H+ from its acid formula ACID Conjugate base Periodic Trend for increasing conjugate base strength weakest acid strongest base Which is the stronger base? Cl _ or I _ HO _ or HS _ HS _. A buffer is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. From what we learned above, OH- wil become the conjugate base and. Acid is HCl, conjugate base is Cl^-. I have the following equation CH3CH2NH3(aq) + H2O(l) ----> H3O(aq) + CH3CH2NH2(aq) and need to determine if the first reactant is an acid or base? I think it is an acid because it lost a hydrogen ion is that correct?. Ok so for question I have to state whether the element/compound is an acid, base, conjugate acid or conjugate base. Example: Acid is HX and conjugate base is X^-. $\ce{CH3CH2NH3Cl}$ is acidic because it is formed from a strong acid ($\ce{HCl}$) and a weak base ($\ce{CH3CH2NH2}$). The energy of the conjugate acid or base determines the strength of the acid or base. Conjugate acid base pairs: Two species related to one another by the presence of a hydrogen ion (in the acid part of the pair) or its absence (in the base part or the pair). The conjugate acid ofCH3CH2NH2will. Let us take the example of bicarbonate ions reacting with water to create carbonic acid and hydronium ions. Below is a graph of a weak acid titration, which is also a graph of the Henderson-Hasselbalch equation, showing how pH changes as acid or base is added. Recall that a strong acid is 100% dissociated in solution (Chapter 4). The higher the pka, the weaker the acid; thus the stronger its conjugate base. What is the conjugate acid in this equation: NH₃(g) + H₂O(l) --> NH₄⁺(aq) + OH⁻(aq) a) NH₃ b) H₂O c) NH₄⁺ d) OH⁻ 2. For example, acetic acid and sodium acetate. asked • 03/18/19 What is the ionization constant at 25 C for the weak acid CH3NH3 +, the conjugate acid of the weak base CH3NH2, Kb = 4. ( Crowe and Bradshaw 2010)Many life forms thrives only in a relatively small pH range so they utilize a buffer solution to. Such substances react with water, removing protons from H 2 O, thereby forming the conjugate acid of the base and OH – ions: [16. According to the conjugate acid-base pair theory, an acid is a proton donor and a base is a proton acceptor. Weak Acid/Weak Base (definitions and eg) Only partially dissociates (ionises) in solution/water (only a small amount of H+ is formed) eg CH3COOH (all carboxylic acids); NH3, CH3CH2NH2 (amines and amides). 1 The Nature of. Therefore, F-, NO. 2S is a weak acid. Topic: Acid -Base Definitions 6. Value of K w for water is 1. A buffer's pH changes very little when a small amount of strong acid or base is added to it. The _____ the weak acid, the _____ the conjugate base. an acid gives its conjugate base and protonation of a base gives the conjugate acid of the base. Which labeled equation shows the reaction of CH3CH2NH2 with H2O and correctly labels the conjugate acid and the conjugate base for the reaction? an you write the balance equation with correct charges?. The strongest acids are at the bottom left, and the strongest bases are at the top right. However, any buffer will lose its effectiveness if too much strong acid or base is added. alchool are stronger acid than amines, therefoee CH3CH2O- is a conjugate base weaker than. The higher the pKb, the weaker the proton accepting power of the base. Water has a limiting effect on the strength of acids and bases. 075 M ethylamine C2H5NH2(aq), the hydroxide ion concentration (OH-) is 6. •A conjugate acid has one more proton than the base has, and a conjugate base one less proton than the acid has. mL of the previous buffer (0. Similarly, HF is the conjugate acid of F –, and F – the conjugate base of HF. However, nitrate is not so weak that it cannot be protonated in sulfuric acid, so NO 3-is of directly measurable base strength in liquid H2SO 4. Give three definitions for acids. 76 x 10 -4phenol 1. Weak Acid/Weak Base (definitions and eg) Only partially dissociates (ionises) in solution/water (only a small amount of H+ is formed) eg CH3COOH (all carboxylic acids); NH3, CH3CH2NH2 (amines and amides). 16 - Saccharin (HC7H4NO3S) is a weak acid with pKa =. Most organic acids are weak acids. Tags: Question 13. Which of the following is a conjugate pair? OH and H30* CH3CH2NH2 and CH3CH3NH3* Question. The ethylammonium ion, CH3CH2NH3+, has a pKa of 10. a) CH3O- b) HC(=O)-O-b is the base of formic acid, it is the formate ion, thus it is quite stable in solution, think sodium formate. The use of conjugate acid-base pairs allows us to make a very simple statement about relative strengths of acids and bases. Acid K abutyric acid 1. The conjugate bases of weak acids are better bases than water. conjugate acid synonyms, conjugate acid pronunciation, conjugate acid translation, English dictionary definition of conjugate acid. Therefore, we conclude that if one has a strong acid, then its conjugate base must be weak. The conjugate base of acetic acid (HA) is (A-) (-) is a superscript. 040 M KOH (aq); (d) household ammonia in which the [OH¯]= 3 x 10 -3 M; (e) 6. The weak base is CH3CH2NH2 and the conjugate acid is CH3CH2NH3^+ and the conjugate base is OH^- for the acid H2O. Conjugate Acids and Bases HCN(aq) + H 2O H Conjugate Acids and Bases HCN is a rather weak acid, K a = 4. which of the following statements is not. 5): Buffer solution = any solution that maintains an approximately constant pH despite small additions of acid or base –> typically a buffer solution contains a weak acid and a weak base that are conjugate to one another. What is the pH of the mixture? The HCL should react with the basic component of the buffer - changing it to its conjugate acid: We need to find out the NEW concentrations of all the species in the buffer solution. Question: Given that Kb for CH3CH2NH2 is 6. The weak bases tends to neutralize any extra acid added to the buffer, and the weak acid tends to neutralize any extra based added. H2CO3 is a weak acid and its conjugate base must be a strong base, H2CO3 = H+(aq) + HCO3-(aq) Eq Constant value is too low the products will not dominate, the reaction has hardly proceded to forward direction. Weak acid produces strong conjugate. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Which species represent a conjugate acid-base pair? A. The strength of a weak organic acid may depend on substituent effects. In this example, the ammonium ion gives up some protons to the solvent, meaning that there is a small excess of H 3 O + in solution. Hydrofluoric acid. Identify the conjugate acid-base pairs in the reaction. This video shows you how to calculate the pH and equilibrium concentrations of all species present, for a solution containing a weak base and the conjugate-acid of that weak base, when the. Conjugate acid-base pair vary by a H+ion. strong acid. When an weak acid-strong base titration is performed, the. In each case write the formula of its conjugate acid, and indicate whether the conjugate acid is a strong acid, a weak acid, or a species with negligible acidity: (a) CH 3 COO –, (b)HCO 3 –, (c) O 2–, (d) Cl –, (e) NH 3. acid + salt of conjugate base. Another thing to note is that CH3CH2NH3 + and CH3CH2NH2 are a acid/conjugate base pair which means that the above equation can be used. d) A weak acid and its conjugate base in solution Question 9 A buffer solution contains ethanoic acid and its conjugate base; the p K a of ethanoic acid is 4. " NH2- is the conjugate base of an extremely weak acid, NH3 (pKa = 35). The basicity of amines is often discussed indirectly in terms of the acidity of their respective conjugate acids. The higher in energy the conjugate base or acid is (wife), the weaker the acid or base is (husband). lithium hydroxide strong base c. 0 x 10-14 and ka and kb are the acid and base constants, respectively. unstable) 4. Get Answer to In general, as base strength increases, conjugate acid strength decreases. This reaction was favored because the conjugate acid of bicarbonate (carbonic acid) has a pKa that was higher than that of benzoic acid, but lower than the pKa of 2. •An example is CH 4. Similarly, a weak base solution with its conjugate acid added from an outside source would also be classified as a buffer. H 2 CO 3 + H 2 O ⇌ H 3 O + + HCO 3- K b = 2. So first of all, you can neglect that the acid CH3COOH will dissociate to CH3COO-, as by the above argument, it only dissociates to a very little extent. 3 x 10-4 = 1. Mix some weak acid with it's conjugate weak base HF, H3P04, NaH2P04 NaHS04 ,Na2S04 CH3COOH, CH3COONa NH4Cl, NH3 2. Arrange the conjugate bases of the acids given in part (a) in order of increasing basicity and explain your reasoning. a C 5 H 5 NH 2 It is the conjugate acid of the weak base pyridine therefore it. 3 base NH 4 + conjugate acid OH- conjugate base Brønsted-Lowry Acids & Bases Identify each species in the following equation as etiher the Brønsted-Lowry acid, the Brønsted-Lowry base, the conjugate acid, or the conjugate base. In 1923, two scientists, Bronsted and Lowry presented a theory on acid-base behaviour. b) a weak base in the presence of a salt that contain the conjugate acid What is the pH of a solution that contains 0. However, with enough acid is base the capacity of the buffer can always be overwhelmed. The strengths of weak bases are measured on the pK b scale. Expert Answer. “Comparable amounts” generally means that the concentrations are within a factor of 10 of each other. Hence, the conjugate base of propanoic acid, is,. (The dissociation reaction reaches equilibrium further to the right, with more X− produced. No, it's goes by degrees. 25 | C5H5N pyridinium ion C5H5NH+ pyridine carbonic acid. That's a short cut for going from an acid to it's conjugate base. In each of the following, identify the conjugate acid/base pairs: HCl + H2O → H3O + + Cl-H3O + + C 2H3O2-' HC 2H3O2 + H2O HC2H3O2. A weak base is a proton acceptor that when put in water will only partially dissociate. 040 M KOH (aq); (d) household ammonia in which the [OH¯]= 3 x 10 -3 M; (e) 6. The strength of conjugate base of an acid is inversely proportional to the acid strength. Thus NH 3 is called the conjugate base of NH 4 +, and NH 4 + is the conjugate acid of NH 3. Weak Acid/Weak Base (definitions and eg) Only partially dissociates (ionises) in solution/water (only a small amount of H+ is formed) eg CH3COOH (all carboxylic acids); NH3, CH3CH2NH2 (amines and amides). True, but this has not been stated or implied. HF, as you recall, is a weak acid, so a little of it will want to dissociate back to F(-) and H(+), but the equilibrium is still mostly to the right, as you can see from the positive value for K. More specifially the proton transfer view is know as the bronsted-lowry defincation of acids and base. OH-is the conjugate base. 010 C End The strong base is converting the weak acid into a weak base (its conjugate base). Buffers can be made by mixing weak acids or bases with salts of their conjugate bases and acids. A weak acid will have a strong conjugate base. When NH3 acts as an acid, it forms its conjugate base by donating a proton. where Kw = 1. 16 - Chloroacetic acid, ClCH2CO2H, is a moderately weak Ch. 12 M Chapter 7 Acids and Bases 7. an acid gives its conjugate base and protonation of a base gives the conjugate acid of the base. Weak Acid/Weak Base (definitions and eg) Only partially dissociates (ionises) in solution/water (only a small amount of H+ is formed) eg CH3COOH (all carboxylic acids); NH3, CH3CH2NH2 (amines and amides). in this reaction CH3CH2NH3 donates an H+ and H20 accepts an H+ ion so ,CH3CH2NH3 is an acid and H20 is a base Identify the conjugate acid or base to the given weak acid or base: Identify the given solution as. For example, Here, is the acid, is the base, is the conjugate acid and is the conjugate base. Therefore F(-) is a strong base. 163 M aqueous solution of sulfurous acid. A weak acid (e. This equation is the approximate solution for calculating the [H+] for any conjugate acid, BH+, of the weak base, B, where Kb < 10-4. Therefore, its conjugate base (F–) is a stronger base than Cl–. 87 CH3CH2COO propanoic acid 9. TABLE OF CONJUGATE ACID-BASE PAIRS Acid Base K a (25 oC) HClO 4 ClO 4 - H 2 SO 4 HSO 4 - HCl Cl- HNO 3 NO 3 - H 3 O + H 2 O H 2 CrO 4 HCrO 4 - 1. A weak acid will react with a strong base to form a basic (pH > 7) solution. For $\pu{550. Furthermore they declare that buffer solutions are very essential to keep the pH value nearly constant in variety of chemical application. That species is an acid and the product of it is conjugate base of that acid. H2CO3 is a weak acid and its conjugate base must be a strong base, H2CO3 = H+(aq) + HCO3-(aq) Eq Constant value is too low the products will not dominate, the reaction has hardly proceded to forward direction. ; C The reaction produces a strong conjugate base and a weak conjugate acid. Substances with negligible acidity do not transfer a proton to water. Find an answer to your question If a buffer has an initial pH of 6. That species is. Answer to: Identify the conjugate acid-base pairs from the following reactions: A. Conjugate Acid. H 2S: remove one H + to make HS–. NH 4 OH will dissociate less in a solution containing NH 4 Cl salt. C) All Bronsted -Lowry acids contain hydrogen. NURS 6320_70 Pathophysiology Midterm Study Guide Spring 2019/20 Below are areas you need to focus on for the midterm exam. Identify the acid and its conjugate base in the reaction above b. If you titrate acetic acid (CH3COOH) with sodium hydroxide (NaOH) the resulting products are the acetate ion (CH3COO-), the sodium ion, and water (see figure 1). Arrange the conjugate bases of the acids given in part (a) in order of increasing basicity and explain your reasoning. K a is the equilibrium constant for the dissociation reaction of a weak acid. Which of the following is a conjugate pair? OH and H30* CH3CH2NH2 and CH3CH3NH3* Question. Relate the strength of a weak acid to the strength of its conjugate base. Although it is weak, it can potentially receive a hydrogen ion from H3O^+, hence giving us the reverse reaction. The weaker the acid is, the stronger its conjugate base. The K a value for conjugate acid is calculated. The conjugation of acids and bases has been discussed earlier. Answer: The weaker the acid, the stronger its conjugate base. Relationship between Ka and Kb for conjugate acid-base pairs Recall that there is an inverse relationship between the strength ofan acid and the strength of its. TYPE 1 (conj. 2 –) with water. Expert Answer. TABLE OF CONJUGATE ACID-BASE PAIRS Acid Base K a (25 oC) HClO 4 ClO 4 – H 2 SO 4 HSO 4 – HCl Cl– HNO 3 NO 3 – H 3 O + H 2 O H 2 CrO 4 HCrO 4 – 1. Previous question. OH-is the conjugate base. This combination also results from a mixture of a weak acid, acetic acid, and its salt, sodium acetate. Assuming you are asking about the base I-, the conjugate acid is HI, hydroiodic acid. This time however, the concentration of conjugate acid is not zero. The conjugate base of a weak acid is a strong base, and the conjugate base of a strong acid is a weak base. In fact, strong acids such as HCl dissociate to produce spectator ions such as Cl-as conjugate bases, whereas weak acids produce weak conjugate bases. Acid name pKa Conjugate base Conjugate base name Acid formula CH3COOH 4. The conjugate base is SiO(OH) 3. An acid and a base which differ only by the presence or absence of a proton are called a conjugate acid-base pair. •The conjugate acid (CA) of a BL base is the acid which forms when the base has accepted a proton. The equilibrium constant for the dissociation for a weak acid that is an equilibrium mixture. D) All Lewis a cids are electron deficient. ACID of a weak base) ( only the SALT of a weak base is put in solution ) For a salt, BHX, of the weak base (B) in water: BHX (s) + H2O BH + + X-(100% ionization!!!, and X-is some anion of a strong acid - it does nothing) Note that BH+ behaves EXACTLY like a weak acid in water (a Type 1 problem for acids) and the equilibria is. Label the acid and base, and the conjugate acid and base in the following reaction. $\begingroup$ @ApoorvPotnis Yeah, I figured that this point wasn't really clear yet. 3 * 10-4 at 25degree C, what is the value of Ka for CH3CH2NH3 at 25 C? How To Relate K_a and K_b for Conjugate Acid-Base Pairs. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory. Write the reaction that occurs, and identify the conjugate acid– base pairs. Answer to: Identify the conjugate acid-base pairs from the following reactions: A. NH 3 is the base. $\ce{CH3CH2NH3Cl}$ is acidic because it is formed from a strong acid ($\ce{HCl}$) and a weak base ($\ce{CH3CH2NH2}$). ; E Water competes with the weak acid to react with. Example: Acid is HX and conjugate base is X^-. For NH4NO3, it is a reaction of a weak base and a strong acid. After losing a proton, the acid species becomes the conjugate base. 0 x 10 -8 M; (b) 0. Question Why will the conjugate base of a weak acid affect pH? Select the correct answer below: O it will react with hydroxide O it will react with water O it will react with hydronium O none of the above Content attribution. Conjugate Acid. (f) HS-? The conjugate base is S2-. Asked May 8, 2020 Conjugate pair consist a group of acid - base pair. This video shows you how to calculate the pH and equilibrium concentrations of all species present, for a solution containing a weak base and the conjugate-acid of that weak base, when the. H 2S: remove one H + to make HS–. That species is an acid and the product of it is conjugate base of that acid. 23 butanoic acid CH3CH2CH2COOH 4. K a is the equilibrium constant for the dissociation reaction of a weak acid. Brönsted acids bases examples. HA + H2O <-> H3O+ + A-Weak acids will be in equilibrium and the equilibrium constant is the Ka. LeChateliers principle: A system in equilibrium will move to the right or to the left to accommodate any stress. 58 x 10-11. Note: basicity for these conjugate base is the reverse of the acidity trend For every Acid, there is a conjugate base To draw a conjugate base, just remove a H+ from its acid formula ACID Conjugate base Periodic Trend for increasing conjugate base strength weakest acid strongest base Which is the stronger base? Cl _ or I _ HO _ or HS _ HS _. Assume that temperature is constant and volumes are additive. The strongest acids are at the bottom left, and the strongest bases are at the top right. Give the conjugate base of an acid.