200 ml of 1 M H2SO4, 300 ml of 3 M HCl and 100 ml of 2 M HCl are mixed and made up to 1 litre. The proton concentration in the resulting solution is:

200 ml of 1 M H2SO4, 300 ml of 3 M HCl and 100 ml of 2 M HCl are mixed and made up to 1 litre. The proton concentration in the resulting solution is ?

A. 0,25 M

B. 1,25 M

C. 2,5 M 

D. 1,5 M 

E. 0,75 M

SOLUTION

H2SO4 contains two H+ ions 

So 200 ml of H2SO4 contains 0,2L×1mol/L×2 = 0,4 mol H+

 

similarly 300 ml of HCL of 3M contains  0,3 L × 3 mol/L × 1 = 0,9 mol H+

 

similarly 100 ml of HCL of 2M contains  0,1L × 2 mol/L × 1 = 0,2 mol H+

Asked: The proton concentration in the resulting solution is ?

Total number of moles = 0,4 + 0,9 + 0,2 = 1,5 mol

Total volume = 200 ml + 300 mL + 100mL = 600mL => 0,6 L

And Concentration of 

[H+] = 1,5/0,6 mol/L = 2,5 mol/L

So, The proton concentration in the resulting solution is 2,5 mol/L.