8. Consider a solution of formic acid (
HCHO
2
) and sodium formate (
NaCHO
2
), at pH=3.70. After the addition of 0.015 moles of
HNO
3
, the pH decreases by 0.12. What are the initial molarities of
HCHO
2
and
CHO
2
-
, if the
K
a
of
HCHO
2
is
1.8x10
-4
?
What is a balanced equation for the equilibrium of the buffered solution before
HNO
3
is added?
a)
HCHO
2
(aq) + H
2
O (l)
H
2
CHO
2
+
(aq) + OH
-
(aq)
b)
CHO
2
-
(aq) + H
2
O (l)
CO
2
2-
(aq) + H
+
(aq)
c)
HCHO
2
(aq)
H
+
(aq) + CHO
2
-
(aq)
d)
CHO
2
-
(aq) + OH
-
(aq)
CH
2
O
3
2-
(aq)