Question

calculate the volumes of 2M and 5M of HCl solutions respectively to be mixed to make 2L of 4M solution?

Answer 1

Total volume of 4M HCl solution = 2 Litre

consider volume of 5M HCl solution = ‘V’ Litre

So, volume of 2M HCl solution = (2-V) Litre

According to equation,

(M1V1 + M2V2) / (V1+V2) = M3

M1 = 5M; V1 = V Litre

M2 = 2M; V2 = (2-V) Litre

M3 = 4M; V1+V2 = 2 Litre

Substitute in equation,

[5 x V + 2 x (2-V)] / 2 = 4

5V + 4 – 2V = 8

3V = 4

So, Volume of 5M HCl solution, V = 1.33 Litre

Then, Volume of 2M HCl solution, 2-V = 2-1.33 = 0.67 Litre