WCB Quiz: Acid/Bases - Strength and Stability

Assume that each of the following reactants can react with liquid water to form H₃O⁺ and the corresponding negatively charged products.

Answer questions 1-9 about these reactants and products.

1. Which product is most stable?

a. CH₃^-

b. NH₂^-.

c. HO^-

d. F^- F is most electronegative element, "likes"electrons most; accomodate and stabilize the negative charge

2. Which product is most reactive?

a. CH₃^- Since the negative is on an element that is not very electronegative

b. NH₂^-.

c. HO^-

d. F^-

3. Which product is most basic?

a. CH₃^- It is most unstable, and hence most likely to act as a proton acceptor to reform CH₄

b. NH₂^-.

c. HO^-

d. F^-

4. Which product is highest in energy?

a. CH₃^- Since it is most unstable and reactive

b. NH₂^-.

c. HO^-

d. F^-

5. Which product is most likely to be formed?

a. CH₃^-

b. NH₂^-.

c. HO^-

d. F^- again because it is most stable, it is most likely to be formed

6. Which reactant is most acidic?

a. CH₄

b. NH₃

c. H₂O

d. HF because it can form the most stable product

7. For which reactant is the reaction with water least favored?

a. CH₄ because it forms the most unstable product

b. NH₃

c. H₂O

d. HF

8. For which reactant does the reaction with water have the most negative ΔG^o_stab?

a. CH₄

b. NH₃

c. H₂O

d. HF because its reaction with water is most favored from a stability perspective

9. For which reactant does the reaction with water have the lowest pK_a?

a. CH₄

b. NH₃

c. H₂O

d. HF because the strongest acid has the lowest pK_a

Assume that each of the following reactants can react with liquid water to form H₃O⁺ and the corresponding negatively charged products. Assume the H's in circles are those protons which transfer to water.

Answer questions 10-18 about these reactants and products.

10. The product from which reactant is second to least stable?

a. 1

b. 2

c. 3 Most stable is product from 4 (resonance), then from 2 (- charge on oxygen), then from 3 (- charge on Nitrogen which is less electronegative than O), and finally the least stable product is from 1 (- charge on C).

d. 4

11. The product from which reactant is least reactive?

a. 1

b. 2

c. 3

d. 4 since it is most stable (resonance) and least reactive.

12. The product from which reactant is least basic?

a. 1

b. 2

c. 3

d. 4 since it is least reactive and less likely to accept a proton to return to original acid

13. The product from which reactant is second highest in energy?

a. 1

b. 2

c. 3 See ans to 10 above.

d. 4

14. The product from which reactant is second most likely to be formed?

a. 1 since it is second most stable product

b. 2

c. 3

d. 4

15. Which reactant is second most acidic?

a. 1 since it forms second most stable product

b. 2

c. 3

d. 4

16. For which reactant is the reaction with water lsecond least favored?

a. 1

b. 2

c. 3 since it forms second least stable product

d. 4

17. For which reactant does the reaction with water have the most positive ΔG^o_stab?

a. 1

b. 2 since it forms the least stable product and is least favored in the forward direction

c. 3

d. 4

18. For which reactant does the reaction with water have the second highest pK_a?

a. 1

b. 2

c. 3 since this acid forms the second least stable product

d. 4