In: Chemistry
If 10mL of .18M Zn(NO3)2 is added to 20.0mL of .26M NaCl and concentration of ZnCl2 is found to be .026M. find Kc
Answer – We are given, [Zn(NO3)2] = 0.18 M , volume = 10 mL
Volume = 20.0 mL , [NaCl] = 0.26 M
At equilibrium, [ZnCl2] = 0.026 M
We know reaction
Zn(NO3)2 + 2 NaCl -----> ZnCl2 + 2 NaNO3
I 0.18 0.26 0 0
C -x -2x +x +2x
E 0.18-x 0.26-2x 0.026 +2x
So, at equilibrium, x = [ZnCl2] = 0.026 M
So, [Zn(NO3)2] = 0.18-x
= 0.18-0.026
= 0.154
[NaCl] = 0.26-2x
= 0.26-2*0.026
= 0.208
[NaNO3] = 2x = 2*0.026 = 0.052 M
So,
Kc = [ZnCl2] [NaNO3]2 / [Zn(NO3)2] [NaCl]2
= (0.026)(0.052)2 / (0.154)(0.208)2
= 0.0106