Chemistry Test Acids and Bases 4

Question 1

What is the pH of a 0.001 M HCl solution at 25°C?

Accepted Answer

3

Answer

HCl is a strong acid, so [H⁺] = 0.001 M = 10⁻³ M; pH = -log(10⁻³) = 3.

Question 2

Which factor causes acid strength to increase going down a group in the periodic table for binary acids (HX)?

Accepted Answer

Decreasing H–X bond strength

Answer

As bond strength decreases going down the group, the H–X bond breaks more easily, releasing H⁺ and increasing acidity.

Question 3

A solution has [H₃O⁺] = 1×10⁻⁹ M. What is its pOH?

Accepted Answer

5

Answer

At 25°C, pH = 9, and since pH + pOH = 14, pOH = 14 − 9 = 5.

Question 4

Which of the following oxoacids is the strongest?

Accepted Answer

HClO₄ (perchloric acid)

Answer

Acid strength of oxoacids increases with the number of oxygen atoms, making HClO₄ the strongest.

Question 5

Which statement about Kw at temperatures above 25°C is correct?

Accepted Answer

Kw increases because autoionization is endothermic

Answer

Water autoionization is endothermic, so higher temperature shifts equilibrium toward products, increasing Kw.

Chemistry Practice Test