Question

Which solution is more acidic and why? 1M HCl or 2M HCl aqueous solution.

Answer 1

Ka for HCl= 1*10^-3

HCl-> H+ + Cl-
1-x       x         x

1*10^-3 = x2/1-x
x2 +1*10^-3x -1*10^-3 =0
x= 0.0311 M

1M HCl -> pH =-log[H+] = -log0.0311 =1.507

HCl-> H+ + Cl-
2-x       x         x

1*10^-3 = x2/2-x
x2 +1*10^-3x -2*10^-3 =0
x= 0.0442 M

2M HCl -> pH =-log[H+] = -log0.0442 =1.354

hence, more acidic will be 2M HCl as it has lower pH than 1M HCl and lower the pH more acidic the solution