chemistry quizz

Question

1. What is the pH of a solution containing 0.25 M HNO₂ and 0.43 M NaNO₂?
2. The solubility of lead chromate (PbCrO₄) is 4.5 *10^-5 g/L. Calculate the solubility product of this compound.

Answer 1

HNO₂ is a weak acid

NaNO₂ is the salt of that weak acid

YOU HAVE A BUFFER SOLUTION

pH = pKa + log [NaNO2]/[HNO2] look up the pKa for HNO2 and substitute and solve for pH

PbCrO₄(s) ==> Pb²⁺(aq) + CrO₄^2-(aq)

Ksp = [Pb²⁺][CrO₄^2-]

Find moles PbCrO₄ in 4.5x10^-5 g and this will be [Pb²⁺] and [CrO₄^2-]. Plug this value into Ksp expression and solve for Ksp.