Q2 A solution has a (OH-) = 4.0x10^-5 M. What are the [H30+) and the pH of the
solution?

[H₃O⁺] = 2.5 × 10⁻¹⁰ M

pH = 9.6

Explanation:

Step 1: Given data

Concentration of OH⁻ in the solution ([OH⁻]): 4.0 × 10⁻⁵ M

Step 2: Calculate the concentration of H₃O⁺ in the solution

Let's consider the self-ionization of water.

2 H₂O(l) ⇄ H₃O⁺(aq) + OH⁻(aq)

The ion-product of water (Kw) is:

Kw = 1.0 × 10⁻¹⁴ = [H₃O⁺] × [OH⁻]

[H₃O⁺] = 1.0 × 10⁻¹⁴/[OH⁻]

[H₃O⁺] = 1.0 × 10⁻¹⁴/4.0 × 10⁻⁵

[H₃O⁺] = 2.5 × 10⁻¹⁰ M

Step 3: Calculate the pH of the solution

We will use the following expression.

pH = -log [H₃O⁺]

pH = -log 2.5 × 10⁻¹⁰

pH = 9.6

the answer is d. 74.02