Question

K_sp of a sparingly soluble salt AB is 1 × 10⁻⁸. When [A⁺] = 10⁻⁴ M, which of the following concentrations of B⁻ will NOT give precipitate of AB?

Options

• 1 × 10⁻¹ M

• 1 × 10⁻⁵ M

• 1 × 10⁻³ M

• 1 × 10⁻² M

Answer 1

1 × 10⁻⁵ M

Explanation:

Precipitation will occur if lP (ionic product) is greater than K_sp·

So, for precipitation not to occur, ionic product should be less than K_sp.

When the concentration of B is 1 × 10⁻⁵ M, the ionic product of 1 × 10⁻⁹ is obtained.

(Here, IP is less than K_sp 1 × 10⁻⁸).