Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 M HCHO₂ with 100.0 mL of 0.20 M LiCHO₂.The K_a for HCHO₂ is 1.8 × 10^-4. A) 3.87 B) 3.74 C) 10.53 D) 3.47 E) 10.13

Question

Quizplus · Accepted Answer

First, we need to write the balanced chemical equation of the reaction between HCHO₂ and LiCHO₂ to determine which species will act as the acid and which will act as the base: HCHO₂ + LiCHO₂ → CHO₂Li + H2O In this reaction, HCHO₂ acts as the acid (donates a proton) and LiCHO₂ acts as the base (accepts a proton) to form CHO₂Li, which is a salt. Next, we need to calculate the moles of acid (HCHO₂) and base (LiCHO₂) in the mixture: moles of HCHO₂ = (0.15 mol/L) x (0.250 L) = 0.0375 mol moles of LiCHO₂ = (0.20 mol/L) x (0.100 L) = 0.0200 mol Since we have more acid than base, the remaining HCHO₂ will be present in the solution. Using the Henderson-Hasselbalch equation, we can calculate the pH of the solution: pH = pKa + log([base]/[acid]) pKa = -log(Ka) = -log(1.8 × 10^-4) = 3.74 [base] = moles of CHO₂Li / total volume of solution = (0.0375 mol) / (0.250 L + 0.100 L) = 0.107 M [acid] = moles of HCHO₂ remaining / total volume of solution = (0.0375 - 0.0200) mol / (0.250 L + 0.100 L) = 0.0675 M pH = 3.74 + log(0.107/0.0675) = 3.47 Therefore, the pH of the solution is 3.47, which is best represented by choice D.

Calculate the PH of a Solution Formed by Mixing 250