A student prepares a solution by combining 100 mL of 0.3M HNO₂ (aq) and 100 mL of 0.3M KNO₂ (aq). Which of the following equations represents the reaction that best helps to explain why adding a few drops of 1.0M HCl (aq) does not significantly change the pH of the solution?
a) HNO₂ + HCl → H₂O + NO₂
b) HNO₂ + KNO₂ → H₂O + KCl
c) HCl + KNO₂ → H₂O + KCl
d) HCl + NO₂ → H₂O + Cl₂