Q: What is the pH of a 0.020 M solution of NaOH? (Assume complete dissociation.)

$$\text{pOH} = -\log(0.020)$$ \\ $$\text{pOH} = 1.70$$ \\ $$\text{pH} = 14 - 1.70 = 12.3$$

Q: Which of the following is a correct ICE table setup for the dissociation of a weak acid HA in water?

Initial: [HA] = c, [H^+] = 0, [A^-] = 0 \\ Change: [HA] = -x, [H^+] = +x, [A^-] = +x \\ Equilibrium: [HA] = c-x, [H^+] = x, [A^-] = x

Q: A 0.50 M solution of propanoic acid ($$\text{C}_2\text{H}_5\text{COOH}) $$has a $$K_a = 1.3 \times 10$$^{-5}$$. What is the pH of the solution? (Assume x$ is small compared to 0.50)

$$x = \sqrt{K_a \times [HA]} = \sqrt{1.3 \times 10$$^{-5}$$ \times 0.50} = 2.55 \times 10$$^{-3}$$ \\ $$\text{pH} = -\log(2.55 \times $$10^{-3}) = 2.59$

Q: What is the pH of a 0.10 M solution of $$NH_3$$ ($$K_b = 1.8 \times 10$$^{-5}$$)?

$$x = \sqrt{K_b \times [NH_3$]} = \sqrt{1.8 \times 10$$^{-5}$$ \times 0.10} = 1.34 \times 10$$^{-3}$$ \\ $$\text{pOH} = -\log(1.34 \times $$10^{-3}) = 2.87$ \\ $$\text{pH} = 14 - 2.87 = 11.13$$

Q: Which of the following is the correct formula for calculating the pH of a strong acid solution?

$$\text{pH} = -\log([\text{H}^+])$$

Q: A solution contains both a strong acid and a strong base. After mixing, the concentration of $$[\text{H}^+] is$$ $$1.0 \times 10$$^{-7}$$ M. What is the pH?

$$\text{pH} = -\log(1.0 \times 10$$^{-7}$$) = 7$$

Q: Which of the following statements is TRUE regarding acids and bases?

Acids increase $$[\text{H}^+] in $$solution.

Q: A 0.200 M solution of $$\text{NH}_4\text{Cl} is $$prepared. Given $$K_b$$ for $$\text{NH}_3 is$$ $$1.8 \times 10$$^{-5}$$, what is the pH of the solution?

$$K_a = \frac{K_w}{K_b} = \frac{1.0 \times 10$$^{-14}$$}{1.8 \times 10$$^{-5}$$} = 5.56 \times 10$$^{-10}$$ \\ x$$ = \sqrt{K_a \times [$$NH_4$$^+]} = \sqrt{5.56 \times $$10^{-10}$$ \times 0.200} = 1.06 \times $$10^{-5}$$ \\ $$\text{pH} = -\log(1.06 \times 10$$^{-5}$$) = 4.98$$

Q: Which of the following is the correct formula for calculating the pOH of a solution?

$$\text{pOH} = -\log([\text{OH}^-])$$

Question 1

Which of the following statements best describes the relationship between pH and pOH in aqueous solutions at 25°C?

Accepted Answer

pH + pOH = 14

Question 2

A solution is prepared by mixing 0.10 M HCl and 0.10 M KOH. What is the resulting pH of the solution?

Accepted Answer

pH = 7

Question 3

What is the pH of a 0.020 M solution of NaOH? (Assume complete dissociation.)

Accepted Answer

$$	ext{pOH} = -\log(0.020)$$ \ $$	ext{pOH} = 1.70$$ \ $$	ext{pH} = 14 - 1.70 = 12.3$$

Question 4

Which of the following is a correct ICE table setup for the dissociation of a weak acid HA in water?

Accepted Answer

Initial: [HA] = c, [H^+] = 0, [A^-] = 0 \ Change: [HA] = -x, [H^+] = +x, [A^-] = +x \ Equilibrium: [HA] = c-x, [H^+] = x, [A^-] = x

Question 5

A 0.50 M solution of propanoic acid ($$	ext{C}_2	ext{H}_5	ext{COOH}) $$has a $$K_a = 1.3 	imes 10$$^{-5}$$. What is the pH of the solution? (Assume x$ is small compared to 0.50)

Accepted Answer

$$x = \sqrt{K_a 	imes [HA]} = \sqrt{1.3 	imes 10$$^{-5}$$ 	imes 0.50} = 2.55 	imes 10$$^{-3}$$ \ $$	ext{pH} = -\log(2.55 	imes $$10^{-3}) = 2.59$

Question 6

Which of the following is NOT a strong acid?

Accepted Answer

CH_3COOH

Question 7

What is the pH of a 0.10 M solution of $$NH_3$$ ($$K_b = 1.8 	imes 10$$^{-5}$$)?

Accepted Answer

$$x = \sqrt{K_b 	imes [NH_3$]} = \sqrt{1.8 	imes 10$$^{-5}$$ 	imes 0.10} = 1.34 	imes 10$$^{-3}$$ \ $$	ext{pOH} = -\log(1.34 	imes $$10^{-3}) = 2.87$ \ $$	ext{pH} = 14 - 2.87 = 11.13$$

Question 8

Which of the following is the correct formula for calculating the pH of a strong acid solution?

Accepted Answer

$$	ext{pH} = -\log([	ext{H}^+])$$

Question 9

A solution contains both a strong acid and a strong base. After mixing, the concentration of $$[	ext{H}^+] is$$ $$1.0 	imes 10$$^{-7}$$ M. What is the pH?

Accepted Answer

$$	ext{pH} = -\log(1.0 	imes 10$$^{-7}$$) = 7$$

Question 10

Which of the following is the conjugate base of $$	ext{HNO}_2$$?

Accepted Answer

$$	ext{NO}_2^-$$

Question 11

Which of the following statements is TRUE regarding acids and bases?

Accepted Answer

Acids increase $$[	ext{H}^+] in $$solution.

Question 12

A 0.200 M solution of $$	ext{NH}_4	ext{Cl} is $$prepared. Given $$K_b$$ for $$	ext{NH}_3 is$$ $$1.8 	imes 10$$^{-5}$$, what is the pH of the solution?

Accepted Answer

$$K_a = \frac{K_w}{K_b} = \frac{1.0 	imes 10$$^{-14}$$}{1.8 	imes 10$$^{-5}$$} = 5.56 	imes 10$$^{-10}$$ \ x$$ = \sqrt{K_a 	imes [$$NH_4$$^+]} = \sqrt{5.56 	imes $$10^{-10}$$ 	imes 0.200} = 1.06 	imes $$10^{-5}$$ \ $$	ext{pH} = -\log(1.06 	imes 10$$^{-5}$$) = 4.98$$

Question 13

Which of the following is a correct method to determine if a salt solution is acidic, basic, or neutral?

Accepted Answer

Check if the cation is from a strong base and the anion is from a strong acid; if so, the solution is neutral.

Question 14

Which of the following is the correct formula for calculating the pOH of a solution?

Accepted Answer

$$	ext{pOH} = -\log([	ext{OH}^-])$$

Question 15

A student mixes equal volumes of 0.10 M HCl and 0.10 M NaOH. What is the expected pH of the resulting solution?

Accepted Answer

pH = 7

Question 16

Which of the following is a strong base?

Accepted Answer

NaOH

Question 17

Which of the following is the conjugate acid of $$	ext{CN}^-$$?

Accepted Answer

$$	ext{HCN}$$

Acid-Base Equilibria and pH Calculations: Study Notes

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