Q: A weak acid, $$HA$$, has a $$K_a of$$ $$1.0 \times 10$$^{-6}$$. If the initial concentration of HA$ is 0.1$ M, which expression best estimates $$[H^+]$$ at equilibrium?

$$[H^+] = \sqrt{K_a \times [HA]_{initial}}$$

Question 1

Which of the following best describes a Brønsted-Lowry acid?

Accepted Answer

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

Question 2

Given the reaction: $$NH_3 + H_2O$$ \rightarrow $$NH_4^+ + OH$$^-$$, which species acts as the Brønsted-Lowry base?

Accepted Answer

$$NH_3$$

Question 3

Which of the following pairs are conjugate acid-base pairs?

Accepted Answer

$$H_2O$$ and $$OH^-$$

Question 4

If the concentration of $$[H_3O^+] in a $$solution is $$1.0 	imes 10$$^{-5}$$ M, what is the pH of the solution?

Accepted Answer

pH = 5.0

Question 5

Which statement is true regarding the relationship between acid strength and the strength of its conjugate base?

Accepted Answer

A weak acid has a strong conjugate base.

Question 6

What is the value of $$K_w ($$the ion product of water) at 25°C?

Accepted Answer

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

Question 7

A solution has $$[OH^-] = 1.0 	imes 10$$^{-3}$$ M. What is the pOH and pH of the solution?

Accepted Answer

pOH = 3.0, pH = 11.0

Question 8

Which of the following is a strong acid?

Accepted Answer

$$HNO_3$$

Question 9

Calculate the pH of a $$0.01 M$$ $$HCl$$ solution.

Accepted Answer

pH = 2.0

Question 10

Which of the following best describes the autoionization of water?

Accepted Answer

$$2H_2O \rightarrow H_3O^+ + OH^-$$

Question 11

A solution has a pH of 8.5. Which statement is correct?

Accepted Answer

The solution is basic.

Question 12

Which of the following is the correct formula for calculating pH?

Accepted Answer

$$pH = -\log[H_3O^+]$$

Question 13

If $$K_a$$ for acetic acid is $$1.8 	imes 10$$^{-5}$$, which statement is true?

Accepted Answer

Acetic acid is a weak acid.

Question 14

Which of the following indicators would be best for measuring the pH of a solution with pH = 4.5?

Accepted Answer

Methyl red (pH 4.4–6.0)

Question 15

A $$0.1 M $$solution of $$NaOH is $$prepared. What is the pH of the solution?

Accepted Answer

pH = 13.0

Question 16

Which of the following is NOT a property of strong acids?

Accepted Answer

They have high pH values.

Question 17

Which equation correctly relates $$pH$$ and $$pOH at 25$$°C?

Accepted Answer

$$pH + pOH = 14.0$$

Question 18

A weak acid, $$HA$$, has a $$K_a of$$ $$1.0 	imes 10$$^{-6}$$. If the initial concentration of HA$ is 0.1$ M, which expression best estimates $$[H^+]$$ at equilibrium?

Accepted Answer

$$[H^+] = \sqrt{K_a 	imes [HA]_{initial}}$$

Question 19

Which of the following is a monoprotic acid?

Accepted Answer

$$HNO_3$$

Question 20

A student measures the pH of a solution using a pH meter and obtains a value of 6.0. What is the $$[H_3O^+]$$ concentration?

Accepted Answer

$$1.0 	imes 10$$^{-6}$$ M

Acid-Base Equilibria: Study Notes for General Chemistry

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