Q: If the concentration of $$[H_3O^+] in a $$solution is $$4.8 \times 10$$^{-5}$$ M, what is the pH?

$$\mathrm{pH = -log(4.8 \times 10$$^{-5}$$) = 4.32}$$

Q: If Ka for HF is $$6.8 \times 10$$^{-4}$$, what is the Kb for F$$^-$$? (K_w = 1$$ \times $$10^{-14} at 25$$°C)

$$K_b = \frac{1 \times 10$$^{-14}$$}{6.8 \times 10$$^{-4}$$} = 1.47 \times 10$$^{-11}$$

Question 1

Which of the following statements best describes a Brønsted–Lowry acid?

Accepted Answer

A substance that donates a proton (H+).

Question 2

Given the reaction: $$\mathrm{NH_3$(aq) + H_2O(l) \rightarrow NH_4$^+(aq) + OH^-(aq)}$$, which species acts as the Brønsted–Lowry base?

Accepted Answer

NH$$_3$$

Question 3

Which of the following is an example of a Lewis acid?

Accepted Answer

BF$$_3$$

Question 4

What is the conjugate acid of F$$^-$$?

Accepted Answer

HF

Question 5

Which of the following salts will produce a basic solution in water?

Accepted Answer

NaF

Question 6

Calculate the pH of a 0.0015 M HCl solution. (Assume complete dissociation.)

Accepted Answer

$$\mathrm{pH = -log(0.0015) = 2.82}$$

Question 7

Which of the following acids is the strongest based on the given Ka values?
CH$$_3$$COOH, Ka = $$1.8 	imes 10$$^{-5}$$
BrCH_2$COOH, Ka = 1.3$$ 	imes $$10^{-3}$$
CCl$$_3$$COOH, Ka = $$3.0 	imes 10$$^{-1}$$

Accepted Answer

CCl$$_3$$COOH

Question 8

What is the relationship between the strength of an acid and its conjugate base?

Accepted Answer

The stronger the acid, the weaker its conjugate base.

Question 9

If the concentration of $$[H_3O^+] in a $$solution is $$4.8 	imes 10$$^{-5}$$ M, what is the pH?

Accepted Answer

$$\mathrm{pH = -log(4.8 	imes 10$$^{-5}$$) = 4.32}$$

Question 10

Which of the following is NOT a strong base?

Accepted Answer

NH$$_3$$

Question 11

What is the value of $$K_w at 25$$°C?

Accepted Answer

$$K_w = 1 	imes 10$$^{-14}$$

Question 12

Which factor most strongly influences acid strength in binary acids within a group?

Accepted Answer

Bond strength

Question 13

A solution contains 0.025 M NH$$_3. $$What is the pH? (Kb for NH$$_3$$ = $$1.8 	imes 10$$^{-5}$$)

Accepted Answer

$$\mathrm{pH = 11.2}$$

Question 14

Which of the following statements about polyprotic acids is correct?

Accepted Answer

The pH of a polyprotic acid solution is determined mainly by the first ionization step if Ka1 and Ka2 differ by a factor of 1000.

Question 15

Which of the following is a real-world example of a weak acid?

Accepted Answer

CH$$_3$$COOH (acetic acid)

Question 16

What is the correct expression for the base-dissociation constant ($$K_b) $$for a weak base?

Accepted Answer

$$K_b = \frac{[BH^+][OH^-]}{[B]}$$

Question 17

Which of the following best explains why perchloric acid (HClO$$_4) is $$stronger than hypochlorous acid (HClO)?

Accepted Answer

HClO$$_4$$ has more oxygen atoms, increasing the acidity.

Question 18

Which of the following is an amphiprotic substance?

Accepted Answer

H$$_2O$$

Question 19

If Ka for HF is $$6.8 	imes 10$$^{-4}$$, what is the Kb for F$$^-$$? (K_w = 1$$ 	imes $$10^{-14} at 25$$°C)

Accepted Answer

$$K_b = \frac{1 	imes 10$$^{-14}$$}{6.8 	imes 10$$^{-4}$$} = 1.47 	imes 10$$^{-11}$$

Acid–Base Equilibria: Classification, Strength, and Calculations

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