The number of moles of nitrous acid used to prepare the solution is 0.0021 moles.
pH of the HNO2 solution = 1. 96
Concentration of the HNO2 solution = Antilog(-1.96) = 0.011 M
We have to set up the ICE table as follows;
HNO2(aq) ⇄ H^+(aq) + NO2^-(aq)
I 0.011 0 0
C -x +x +x
E 0.011 - x x x
The dissociation constant of the acid is 5.0 × 10−4
Hence;
5.0 × 10−4 = x^2/ 0.011 - x
5.0 × 10−4(0.011 - x ) = x^2
5.5 × 10^-6 - 5.0 × 10^-4x = x^2
x^2 + 5.0 × 10^-4x - 5.5 × 10^-6 = 0
x= 0.0021 M
The concentration of the acid (H^+) in the solution is 0.0021 M. The number of moles of the acid is obtained from;
0.0021 M × 1 L = 0.0021 moles
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