pH of the resulting solution will be 2.9.
Explanation:
25 ml of 0.01 M NaOH contains = 25 × 0.01 = 0.25 milli moles
75 ml of 0.005 M HCl contains = 75 × 0.005 = 0.375 milli moles
(0.375 - 0.25) = 0.125 milli moles
0.125 milli moles of each NaOH and HCl may neutralize each other and so the final solution may contain 0.125 milli moles of HCl.
In 1 L or 1000 ml of the solution, the quantity of HCl present is 0.125 × 10 = 1.25 milli moles
It can be converted to moles by dividing milli moles by 1000, we will get,
0.00125 moles
So the concentration of Hydrogen ions, [H⁺] = 0.00125 M
pH = -log₁₀[H⁺]
= -log₁₀[0.00125]
= 2.9
So pH of the resulting solution will be 2.9.
