Question

A lab assistant prepared a solution by adding a calculated quantity of HCl gas at 25°C to get a solution with [H₃O⁺]= 4 × 10⁻⁵ M. Is the solution neutral (or) acidic (or) basic.

Answer 1

[H₃O⁺] = 4 × 10⁻⁵ M

pH = – log₁₀ [H₃O⁺]

pH = – log₁₀ [4 × 10⁻⁵]

pH = – log₁₀ [4] – log₁₀ [10⁻⁵]

pH = – 0.6020 – (– 5)

= – 0.6020 + 5

pH = 4.398

Therefore, the solution is acidic.

Since pH is less than 7, the solution is acidic.