In: Chemistry
Recalculate the percent dissociation of 0.19M HN3 in the presence of 0.19M HCl.
Recalculate the percent dissociation of 0.19M HN3 in the presence of 0.19M HCl.
Given : Molarity of HN3 = 0.19 M , [HCl]= 0.19 M
We know HCl is strong acid so it ionizes completely.
The[ H3O+ ]= [HCl]= 0.19 M
To show the dissociation of HN3, we have to show its reaction with water. and then by using ICE chart we have to find final concentration of H3O+ (at equilibrium )
HN3 (aq) + H2O (l) -----> H3O+ (aq) + N3- (aq)
I 0.19 0.19 0
C -x +x +x
E (0.19-x) (0.19 +x) x
We look for ka value for HN3 in reference table.
Ka = 1.9E-5
Equilibrium constant expression.
Ka = (1.9E-5) = (x+0.19) x / (0.19-x)
Now we have t solve for x
x in the denominator and numerator is neglected by considering 5% approximation
1.9 E-5 = 0.19 x / 0.19
x = 1.9 E-5
Percent dissociation = x/ [HN3] * 100
= 1.9E-5 / 1.9 * 100
= 1 E-5 * 100 = 1E-3 %
Or 0.001 %