10. Consider a solution of formic acid (HCHO2) and sodium formate (NaCHO2), at pH=3.70. After the addition of 0.015 moles of HNO3, the pH decreases by 0.12. What are the initial molarities of HCHO2 and CHO2-, if the Ka of HCHO2 is 1.8x10-4?

Equilibrium system:

HCHO2 (aq) H+ (aq) + CHO2- (aq)

x = [HCHO2], y = [CHO2-], 0.912x = y

Having the relationship between the original concentrations of the buffer components, what is the balanced equation of the reaction that occurs with HNO3?

a) HCHO2 (aq) + H+ (aq) H2CHO2+ (aq)
b) HCHO2 (aq) + H2O (aq) HCH3O3 (aq)
c) CHO2- (aq) + H+ (aq) HCHO2 (aq)
d) CHO2- (aq) + H2O (aq) HCHO2 (aq) + OH- (aq)