In: Chemistry
Be sure to answer all parts. At what concentration does hydrocyanic acid (Ka = 4.9 × 10−10) exhibit 0.05 percent ionization? Assume the temperature to be 25°C. × 10 M At what concentration does hydrocyanic acid exhibit 0.10 percent ionization? Assume the temperature to be 25°C. × 10 M At what concentration does hydrocyanic acid exhibit 0.15 percent ionization? Assume the temperature to be 25°C. × 10 M
part 1)
Ka = 4.9 x 10^-10
% ionization = 0.05 %
HCN (aq) -------------> H+ (aq) + CN- (aq)
x 0 0
x- 0.05x/100 0.05x/100 0.05x/100
Ka = (0.05x/100)^2 / (x -0.05x/100 )
4.9 x 10^-10 = ((0.05)^2 x / 100) x 1 / 99.95
x = 2.0 x 10^-3
concentration of HCN = 2.0 x 10^-3 M
part 2)
% ionization = 0.10 %
Ka = (0.10 x /100)^2 / (x - 0.10x / 100)
4.9 x 10^-10 = (0.10)^2 x / 100 x (1 / 99.90)
x = 4.9 x 10^-4
concentration of HCN = 4.9 x 10^-4 M
part 3)
% ionization = 0.15 %
concentration = 2.2 x 10^-4 M