Concept explainers
Interpretation: The direction of equilibrium in the indicated reaction should be identified.
Concept introduction: In accordance with Bronsted definition an acid can act as a proton donor and a base can act as a proton acceptor. Thus in a typical acid-base reaction, the fundamental principle is a lone pair of base reaches out for an acidic proton. Similar curved arrows are used to show the movement of electrons. After deprotonation, the species left with a negative charge is referred as the conjugate base of acid while the other with a positive charge is termed conjugate acid of given base. For example;
The strength of various conjugate acid-base pairs varies inversely to one another; the strong acid has a weak conjugate base and the strong base has weak conjugate acid and vice-versa.
The order of acidic strength of various alcohols is as follows:
For tertiary alcohols, the steric bulk is maximum that leads to inhibition in solvation of
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Organic Chemistry: Structure and Function
- Complete each of these reactions by filling in the blanks. Predict whether each reaction is product-favored or reactant-favored, and explain your reasoning. (a) _________ (aq) + Br(aq) NH3(aq) + HBr(aq) (b) CH3COOH(aq) + CN(aq) ________ (aq) + HCN(aq) (c) ________ (aq)+H2O () NH3(aq) + OH(aq)arrow_forwardFor conjugate acidbase pairs, how are Ka and Kb related? Consider the reaction of acetic acid in water CH3CO2H(aq)+H2O(l)CH3CO2(aq)+H3O+(aq) where Ka = 1.8 105 a. Which two bases are competing for the proton? b. Which is the stronger base? c. In light of your answer to part b. why do we classify the acetate ion (CH3CO2) as a weak base? Use an appropriate reaction to justify your answer. In general, as base strength increases, conjugate acid strength decreases. Explain why the conjugate acid of the weak base NH3 is a weak acid. To summarize, the conjugate base of a weak acid is a weak base and the conjugate acid of a weak base is a weak acid (weak gives you weak). Assuming Ka for a monoprotic strong acid is 1 106, calculate Kb for the conjugate base of this strong acid. Why do conjugate bases of strong acids have no basic properties in water? List the conjugate bases of the six common strong acids. To tie it all together, some instructors have students think of Li+, K+, Rb+, Cs+, Ca2+, Sr2+, and Ba2+ as the conjugate acids of the strong bases LiOH, KOH. RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. Although not technically correct, the conjugate acid strength of these cations is similar to the conjugate base strength of the strong acids. That is, these cations have no acidic properties in water; similarly, the conjugate bases of strong acids have no basic properties (strong gives you worthless). Fill in the blanks with the correct response. The conjugate base of a weak acid is a_____base. The conjugate acid of a weak base is a_____acid. The conjugate base of a strong acid is a_____base. The conjugate acid of a strong base is a_____ acid. (Hint: Weak gives you weak and strong gives you worthless.)arrow_forwardWhat are the equilibrium concentrations of acetic acid, the acetate ion, and H3O+ for a 0.10 M solution of acetic acid (K2 = 1.8 105)? What is the pH of the solution?arrow_forward
- Consider the following chemical reaction at equilibrium: NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + HO⁻(aq) If one drop of aqueous sodium hydroxide (NaOH) is added, in which direction will the equilibrium shift? A) reactants B) products C) neither the reactants nor the productsarrow_forwardConsider the following equilibrium: HNO2(aq) + H2O (l) ⇌ H3O+(aq) + NO2-(aq) In which direction (if any) will the equilibrium shift if: KNO2 is added? NaOH is added?arrow_forwardWhen propionic acid is reacted with sodium hydroxide, as shown below, what can be said about the reaction after equilibrium has been reached? HO, NaOH + H,0 + Na propionic acid sodium hydroxide sodium propionate NaOH = Na® OH %3D O the concentration of propionic acid and sodium propionate are approximately equal the concentration sodium propionate is much greater than the concentration of propionic acid the concentration of propionic acid is much greater than the concentration of sodium propionatearrow_forward
- In which direction would the reaction have to run in order to rebalance the ratios of CO2 and H2 O to H+ and HCO3 − when CO2 levels are lower than normal?CO2CO2+ H2O ⇌ H2CO3 ⇌ H++ HCO3−arrow_forwardWhat is the equilibrium expression for: 2NH3 ⇌ N2 + 3H2arrow_forwardAcetic acid is a weak acid, meaning it does not fully dissociate in water. Instead, there is an equilibrium between the dissolved but undissociated molecule and the component ions: HOAc (aq) + H2O (l) ⇌ H3O+ (aq) + OAc– (aq)OAc– is an abbreviation for the acetate ion, CH3COO–, and H3O+ is the hydronium ion (lone protons, H+ (aq), do not exist!). (d) When starting with completely un-dissociated acetic acid, is it accurate to assume that [HOAc]0 = [HOAc]eq? Why or why not? (e) A highly concentrated acetic acid solution contains 15.0M acetic acid at equilibrium. What are the equilibrium concentrations of the hydronium and acetate ions in this solution? (f) Creating the concentrated acetic acid solution by dissolving liquid HOAc in water raises the temperature of the water by about 5°C from room temperature. At 50°C, do you expect the solution to contain more or less acetate ion OAc– than what you calculated in (c)? Why?arrow_forward
- Acetic acid is a weak acid, meaning it does not fully dissociate in water. Instead, there is an equilibrium between the dissolved but undissociated molecule and the component ions: HOAc (aq) + H2O (l) ⇌ H3O+ (aq) + OAc– (aq)OAc– is an abbreviation for the acetate ion, CH3COO–, and H3O+ is the hydronium ion (lone protons, H+ (aq), do not exist!). (a) Write the equilibrium constant expression for the dissociation of acetic acid. (b) Vinegar sold commercially is typically 0.8 − 1.0 M acetic acid. A 1.00 M solution of acetic acid is measured by its pH to have an equilibrium concentration of 4.19×10−3 M for both acetate ions and hydronium ions at room temperature. Assuming [HOAc]0 = 1.00M, what is the equilibrium concentration of undissociated acetic acid [HOAc]eq to the correct number of significant figures? (c) What is the value of the equilibrium constant Keq for the dissociation according to the concentrations from part (b)? (d) When starting with completely un-dissociated…arrow_forwardWrite the formula for the K eq for the following reaction: N 2(g) +3H 2(g) ->2NH3(g)arrow_forwardSwimming pool disinfectants produce hypochlorous acid upon dissolution. The weak acid ionizes as follows: HClO (aq) ⇄ H+ (aq) + ClO‒ (aq) Ka=3.0 x 10 ‒8 As strong oxidizing agents, both acid and its conjugate base kill bacteria. However, too high [HClO] is irritating to swimmers’ eyes and too high [ClO‒] will cause the ions to decompose in sunlight. The recommended pH to circumvent both problems is 7.8. Determine the ratio of the weak acid and its conjugate base at this pH.arrow_forward
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