Q: If the pH of a solution is 5.25, what is the hydronium ion concentration?

$$[\mathrm{H_3O^+}] = 5.6 \times 10$$^{-6}$$\ \mathrm{M}$$

Q: Which of the following best explains why the pH of pure water at 25°C is 7?

Because $$[\mathrm{H_3O^+}] = [\mathrm{OH^-}] = 1.0 \times 10$$^{-7}$$\ \mathrm{M}$$

Question 1

Which of the following best describes the Brønsted-Lowry definition of an acid?

Accepted Answer

A substance that donates a proton (H$$^+) to $$another substance.

Question 2

Which of the following pairs is a correct conjugate acid-base pair?

Accepted Answer

NH$$_4^+$$ and NH$$_3$$

Question 3

Given the auto-ionization of water: $$2\,\mathrm{H_2O}(l) \rightleftharpoons \mathrm{H_3O^+}(aq) + \mathrm{OH^-}(aq)$$, what is the value of $$K_w at 25$$°C?

Accepted Answer

$$1.0 	imes 10$$^{-14}$$

Question 4

A solution has a hydronium ion concentration of $$[\mathrm{H_3O^+}] = 2.5 	imes 10$$^{-4}$$\ \mathrm{M}. $$What is the pH of the solution?

Accepted Answer

$$pH = 3.60$$

Question 5

Which of the following substances is amphiprotic?

Accepted Answer

H$$_2O$$

Question 6

What is the pOH of a solution with $$[\mathrm{OH^-}] = 3.2 	imes 10$$^{-5}$$\ \mathrm{M}$$?

Accepted Answer

$$pOH = 4.49$$

Question 7

A 0.50 M solution of acetic acid ($$\mathrm{CH_3COOH}) $$has $$K_a = 1.76 	imes 10$$^{-5}$$. What is the pH of the solution? (Assume x$$ \ll 0.50$$)

Accepted Answer

$$pH = 2.37$$

Question 8

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

Accepted Answer

NaF

Question 9

If the pH of a solution is 5.25, what is the hydronium ion concentration?

Accepted Answer

$$[\mathrm{H_3O^+}] = 5.6 	imes 10$$^{-6}$$\ \mathrm{M}$$

Question 10

Which of the following equations correctly represents the ionization of ammonia ($$\mathrm{NH_3$}) in $$water?

Accepted Answer

$$\mathrm{NH_3$}(aq) + \mathrm{H_2O}(l) \rightleftharpoons \mathrm{NH_4$^+}(aq) + \mathrm{OH^-}(aq)$$

Question 11

A solution has a pOH of 2.75. What is the pH of the solution at 25°C?

Accepted Answer

$$pH = 11.25$$

Question 12

Which of the following statements is true regarding the relationship between $$K_a$$ and $$K_b$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 13

Which of the following best explains why the pH of pure water at 25°C is 7?

Accepted Answer

Because $$[\mathrm{H_3O^+}] = [\mathrm{OH^-}] = 1.0 	imes 10$$^{-7}$$\ \mathrm{M}$$

Question 14

A 0.50 M solution of ammonia ($$\mathrm{NH_3$}) $$has $$K_b = 1.79 	imes 10$$^{-5}$$. What is the pH of the solution? (Assume x$$ \ll 0.50$$)

Accepted Answer

$$pH = 11.63$$

Question 15

Which of the following is the correct expression for the acid dissociation constant ($$K_a) $$for acetic acid ($$\mathrm{CH_3COOH}$$)?

Accepted Answer

$$K_a = \dfrac{[\mathrm{CH_3COO^-}][\mathrm{H_3O^+}]}{[\mathrm{CH_3COOH}]}$$

Question 16

Which of the following best describes the behavior of an amphiprotic substance?

Accepted Answer

It can act as either an acid or a base depending on the reaction.

Question 17

A salt solution is prepared by dissolving sodium acetate ($$\mathrm{NaCH_3COO}) in $$water. Predict the pH of the solution.

Accepted Answer

The solution will be basic because acetate ions hydrolyze to produce OH$$^-.$$

Question 18

Which of the following is the correct relationship between pH and pOH at 25°C?

Accepted Answer

$$pH + pOH = 14$$

Question 19

A solution is prepared by dissolving ammonium chloride ($$\mathrm{NH_4Cl}) in $$water. Which of the following best describes the resulting solution?

Accepted Answer

The solution will be acidic because $$\mathrm{NH_4$^+}$$ acts as a weak acid.

Acids and Bases Equilibrium: Bronsted-Lowry Theory, pH Calculations, and Salt Solutions

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