11.8 mL of 0.30 M HCl is added to a 122.0-mL sample of 0.210 M HNO₂ (K_a for HNO₂ = 4.0*10^-⁴). What is the equilibrium concentration of NO₂^- ions?

Question

Quizplus · Accepted Answer

The equilibrium concentration of NO2- ions can be calculated using the initial concentrations and the reaction stoichiometry. The HCl will react with HNO2 to form NO2- and H2O. The moles of HCl added are 0.00354 mol, and the moles of HNO2 initially present are 0.02562 mol. After the reaction, the concentration of NO2- is determined by the equilibrium expression using the given Ka value. The correct concentration is 2.9 x 10^-3 M.

118 ML of 0