Q: A solution of ammonia ($$NH_3) $$has a pH of 11.09. What is the concentration of hydroxide ions, $$[OH^-]$$, in this solution?

$$[OH^-] = 8.2 \times 10$$^{-12}$$ mol/L

Q: Given $$K_w = 1.0 \times 10$$^{-14}$$ at 25°C, what is the K_b$ for the conjugate base of a weak acid with K_a = 2.0$$ \times $$10^{-5}$$?

$$K_b = 5.0 \times 10$$^{-10}$$

Q: A solution has a pH of 2.0. What is the hydrogen ion concentration, $$[H^+]$$, in this solution?

$$[H^+] = 1.0 \times 10$$^{-2}$$ mol/L

Q: A solution of ethanoic acid has a pH of 5.30. What is the $$[H^+] in $$this solution?

$$[H^+] = 5.0 \times 10$$^{-6}$$ mol/L

Q: Which of the following is true for a neutral aqueous solution at 25°C?

$$[H^+] = [OH^-] = 1.0 \times 10$$^{-7}$$ mol/L

Question 1

Which of the following statements best explains why acetylsalicylic acid (ASA) is considered a stronger acid than acetaminophen, based on their $$K_a$$ values?

Accepted Answer

ASA has a higher $$K_a$$ value, so it ionizes more in water.

Question 2

A solution of ammonia ($$NH_3) $$has a pH of 11.09. What is the concentration of hydroxide ions, $$[OH^-]$$, in this solution?

Accepted Answer

$$[OH^-] = 8.2 	imes 10$$^{-12}$$ mol/L

Question 3

Which of the following best describes the relationship between the strength of an acid and the strength of its conjugate base?

Accepted Answer

A strong acid has a very weak conjugate base.

Question 4

Given $$K_w = 1.0 	imes 10$$^{-14}$$ at 25°C, what is the K_b$ for the conjugate base of a weak acid with K_a = 2.0$$ 	imes $$10^{-5}$$?

Accepted Answer

$$K_b = 5.0 	imes 10$$^{-10}$$

Question 5

A student uses red cabbage juice as an indicator and observes a green color in a solution. What can be inferred about the solution's pH?

Accepted Answer

The solution is basic (pH \u003e 7).

Question 6

Which of the following equations correctly relates $$K_w$$, $$K_a$$, and $$K_b$$ for a conjugate acid-base pair?

Accepted Answer

$$K_w = K_a 	imes K_b$$

Question 7

A solution has a pH of 2.0. What is the hydrogen ion concentration, $$[H^+]$$, in this solution?

Accepted Answer

$$[H^+] = 1.0 	imes 10$$^{-2}$$ mol/L

Question 8

Which of the following best explains why Group 2 hydroxides like $$Ca(OH)_2$$ are used in environmental applications such as flue gas 'scrubbers'?

Accepted Answer

They are strong bases but only slightly soluble, allowing controlled neutralization.

Question 9

If the pH of a solution is 4, what is its pOH at 25°C?

Accepted Answer

pOH = 10

Question 10

Which of the following substances is most likely to turn blue litmus paper red?

Accepted Answer

A solution of lemon juice

Question 11

A solution has $$[OH^-] = 1.0$$ mol/L at 25°C. What are its pOH and pH values?

Accepted Answer

pOH = 0.00; pH = 14.00

Question 12

Which of the following best describes the autoionization of water?

Accepted Answer

Two water molecules react to form $$H_3O^+$$ and $$OH^-$$ ions.

Question 13

A solution of ethanoic acid has a pH of 5.30. What is the $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 5.0 	imes 10$$^{-6}$$ mol/L

Question 14

Which of the following is true for a neutral aqueous solution at 25°C?

Accepted Answer

$$[H^+] = [OH^-] = 1.0 	imes 10$$^{-7}$$ mol/L

Question 15

Which of the following best describes an organic base?

Accepted Answer

A compound that contains nitrogen with a lone pair and increases $$[OH^-].$$

Question 16

A pH meter is used to measure the pH of two solutions: one is lemon juice and the other is ammonia. Which of the following best describes the expected readings?

Accepted Answer

Lemon juice will have a lower pH than ammonia.

Question 17

Which of the following is the correct formula for calculating pH from hydrogen ion concentration?

Accepted Answer

$$pH = -\log[H^+]$$

Question 18

A solution has a pOH of 2.41. What is its pH and is the solution acidic, basic, or neutral?

Accepted Answer

pH = 11.59; basic

Question 19

Which of the following best explains why weak acids and weak bases are common in biological systems?

Accepted Answer

They only partially ionize, allowing for controlled pH changes.

Lesson 8.2: Strong and Weak Acids and Bases: Properties, Equilibria, and pH Calculations

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