75 ~mL of 0.2 M HCl is mixed with 25 ~mL of 1 M HCl . To this solution, 300 ~mL of distilled water is added. What is the pH of the resultant solution?

Step-by-step solution

aligned V₁ & =75 ~mL , V₂=25 ~mL M₁ & =0.2 M , M₂=1 M V₃ & =300 ~mL , pH =? V & =V₁+V₂=75+25=100 ~mL M & = V₁ M₁+V₂ M₂ V₁+V₂ = 75 0.2 25+1 75+25 =0.4 M aligned Total volume aligned V^ =V₁+V₂+V₃ & =75+25+300=400 ~mL M V & =M^ V^ 0.4 100 & =M^ 400 M & =0.1 M aligned Concentration of HCl =0.1=10⁻¹ pH =- ₁₀ [ H ⁺ ]=1