Q: Which of the following is the correct form of the Henderson-Hasselbalch equation?

$$pH = pK_a + \log \left( \dfrac{[\text{conjugate base}]}{[\text{acid}]} \right)$$

Question 1

Which of the following statements best explains why the equilibrium in the reaction between acetic acid ($$\mathrm{CH_3COOH}$$, $$\mathrm{p}K_a = 4.76) $$and sodium hydroxide ($$\mathrm{NaOH}$$, $$\mathrm{p}K_a \u003e 15) $$favors the formation of acetate ion ($$\mathrm{CH_3COO^-}$$)?

Accepted Answer

Because the equilibrium favors the formation of the weaker acid, and acetic acid is stronger than water.

Question 2

Given the reaction: $$\mathrm{CH_3COOH} + \mathrm{Cl^-} \rightarrow \mathrm{CH_3COO^-} + \mathrm{HCl}$$, which species acts as the conjugate acid?

Accepted Answer

$$\mathrm{HCl}$$

Question 3

Which of the following is the correct form of the Henderson-Hasselbalch equation?

Accepted Answer

$$pH = pK_a + \log \left( \dfrac{[	ext{conjugate base}]}{[	ext{acid}]} ight)$$

Question 4

A solution contains equal concentrations of acetic acid and its conjugate base. If $$pK_a = 4.76$$, what is the pH of the solution?

Accepted Answer

$$pH = 4.76$$

Question 5

Which of the following acids is the strongest, based on $$pK_a$$ values?

Accepted Answer

Aspirin ($$pK_a = 3)$$

Question 6

If the $$pH of a $$solution containing aspirin ($$pK_a = 3) is$$ $$2$$, what is the ratio of conjugate base to acid?

Accepted Answer

$$0.1$$

Question 7

Which of the following best describes a Lewis acid?

Accepted Answer

A species that accepts an electron pair.

Question 8

In the reaction between $$\mathrm{$$AlCl_3$$}$$ and $$\mathrm{CH_3O^-}$$, which species acts as the Lewis base?

Accepted Answer

$$\mathrm{CH_3O^-}$$

Question 9

Which of the following statements is true regarding the relationship between acid strength and conjugate base strength?

Accepted Answer

A strong acid has a weak conjugate base.

Question 10

Given the following reaction: $$\mathrm{CH_3CH_2O^-} + \mathrm{CH_3NH_3^+} \rightarrow \mathrm{CH_3CH_2OH} + \mathrm{CH_3NH_2}$$, and $$pK_a$$ values of $$16$$ for ethanol and $$10.7$$ for methylamine, which direction does the equilibrium favor?

Accepted Answer

Formation of $$\mathrm{CH_3CH_2OH}$$ and $$\mathrm{CH_3NH_2}$$

Question 11

Calculate the ratio $$\dfrac{[\mathrm{RCOO^-}]}{[\mathrm{RCOOH}]} at$$ $$pH = 1$$ for a carboxylic acid with $$pK_a = 3.49.$$

Accepted Answer

$$3.24 	imes 10$$^{-3}$$

Question 12

Which of the following is the correct electron configuration for aluminum after promotion and hybridization for $$\mathrm{$$AlCl_3$$}$$?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^1$$ $$3p^2$$ $$3d^0$$

Question 13

Which of the following species is the strongest base according to the relative strengths diagram?

Accepted Answer

$$\mathrm{R-O^-}$$

Question 14

In the context of Le Chatelier's Principle, what will happen if more acid is added to a buffer solution containing acetic acid and acetate?

Accepted Answer

The concentration of acetate will decrease as it reacts with the added acid.

Question 15

Which of the following is true about the $$pK_a$$ values of carboxylic acids, alcohols, and amines?

Accepted Answer

Alcohols have higher $$pK_a$$ values than carboxylic acids.

Question 16

Which of the following is the correct formal charge calculation for nitrogen in $$\mathrm{CH_3NH_2}$$?

Accepted Answer

$$FC_N = 5 - (4 + \frac{1}{2}(4)) = -1$$

Question 17

Which of the following best describes the effect of increasing the ratio $$\dfrac{[	ext{conjugate base}]}{[	ext{acid}]} in a $$buffer solution?

Accepted Answer

The pH increases.

Question 18

Which of the following is a correct statement about the relationship between $$pK_a$$ and acid strength?

Accepted Answer

A lower $$pK_a$$ value indicates a stronger acid.

Acid-Base Chemistry in Organic Compounds: Strengths, Equilibria, and Lewis Theory

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