Q: If the $$\mathrm{pH} of a $$solution is $$4.597$$, what is the $$\mathrm{[H_3O^+]}$$?

$$2.53 \times 10$$^{-5}$$\ \mathrm{M}$$

Q: Which of the following acids is the strongest based on their $$K_a$$ values?

Nitrous acid, $$K_a = 4.5 \times 10$$^{-4}$$

Question 1

Which of the following statements best distinguishes a strong electrolyte from a weak electrolyte in aqueous solution?

Accepted Answer

Strong electrolytes ionize or dissociate completely in water, while weak electrolytes ionize or dissociate only partially.

Question 2

What is the concentration of $$\mathrm{OH^-}$$ ions in a $$0.020\ \mathrm{M}$$ solution of strontium hydroxide, $$\mathrm{Sr(OH)_2}$$, assuming complete dissociation?

Accepted Answer

$$0.040\ \mathrm{M}$$

Question 3

Given the autoionization of water at $$25^\circ\mathrm{C}$$, $$\mathrm{K_w} = 1.0 	imes 10$$^{-14}$$, what is the $$\mathrm{pH}$$ of pure water at this temperature?

Accepted Answer

$$7.00$$

Question 4

A $$0.050\ \mathrm{M}$$ solution of $$\mathrm{$$HNO_3$$} is $$prepared. What is the $$\mathrm{[H_3O^+]} in $$this solution?

Accepted Answer

$$0.050\ \mathrm{M}$$

Question 5

Calculate the $$\mathrm{pH} of a $$solution with $$\mathrm{[H_3O^+]} = 0.030\ \mathrm{M}.$$

Accepted Answer

$$1.52$$

Question 6

If the $$\mathrm{pH} of a $$solution is $$4.597$$, what is the $$\mathrm{[H_3O^+]}$$?

Accepted Answer

$$2.53 	imes 10$$^{-5}$$\ \mathrm{M}$$

Question 7

Which of the following acids is the strongest based on their $$K_a$$ values?

Accepted Answer

Nitrous acid, $$K_a = 4.5 	imes 10$$^{-4}$$

Question 8

A $$0.12\ \mathrm{M}$$ solution of a weak monoprotic acid, $$HY$$, is $$5.0\%$$ ionized. What is the value of its ionization constant, $$K_a$$?

Accepted Answer

$$3.0 	imes 10$$^{-4}$$

Question 9

Which of the following best describes the relationship between $$K_a$$ and $$K_b$$ for a conjugate acid-base pair in water at $$25^\circ\mathrm{C}$$?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 10

A $$0.10\ \mathrm{M}$$ solution of sodium hypochlorite ($$\mathrm{NaClO}) is $$prepared. Given $$K_b$$ for $$\mathrm{ClO^-} is$$ $$2.9 	imes 10$$^{-7}$$, what is the expected $$\mathrm{pH}$$ of the solution?

Accepted Answer

$$10.5$$

Question 11

Which of the following salts will produce a neutral solution when dissolved in water?

Accepted Answer

Potassium nitrate, $$\mathrm{$$KNO_3$$}$$

Question 12

Which of the following best explains why a solution of ammonium bromide ($$\mathrm{NH_4Br}) is $$acidic?

Accepted Answer

The ammonium ion ($$\mathrm{NH_4$^+}) $$acts as a weak acid and donates a proton to water, increasing $$\mathrm{[H_3O^+]}.$$

Question 13

A $$0.15\ \mathrm{M}$$ solution of acetic acid ($$K_a = 1.8 	imes 10$$^{-5}$$) is prepared. Which of the following is closest to the percent ionization of acetic acid in this solution?

Accepted Answer

$$1.1\%$$

Question 14

Which of the following statements about polyprotic acids is correct?

Accepted Answer

The first ionization constant ($$K_{a1}) is $$always greater than the second ($$K_{a2}$$), which is greater than the third ($$K_{a3}).$$

Question 15

Which of the following best describes the pH of a $$0.10\ \mathrm{M}$$ solution of sodium fluoride ($$\mathrm{NaF}$$), given that $$K_a$$ for HF is $$7.2 	imes 10$$^{-4}$$?

Accepted Answer

The solution is basic because $$\mathrm{F^-}$$ hydrolyzes to produce $$\mathrm{OH^-}.$$

Question 16

A solution is prepared by dissolving equal concentrations of acetic acid ($$K_a = 1.8 	imes 10$$^{-5}$$) and ammonia (K_b = 1.8$$ 	imes $$10^{-5}). $$What is the expected pH of the solution?

Accepted Answer

$$7.00$$

Question 17

Which of the following is the correct expression for the hydrolysis constant ($$K_b) of $$the hypochlorite ion ($$\mathrm{ClO^-}$$), given $$K_a$$ for $$\mathrm{HClO}$$?

Accepted Answer

$$K_b = \dfrac{K_w}{K_a}$$

Question 18

Which of the following best describes the effect of increasing the concentration of a weak acid on its percent ionization?

Accepted Answer

Percent ionization decreases as the concentration of the weak acid increases.

Ionic Equilibria: Acids and Bases (Chapter 18 Study Notes)

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