Question

For given solution in the questions molarity can be treated as molality and solute(s) is/are nonvolatile in nature. Given that : Ka of CH3COOH=10−5;Kf= Molal depression constant Ka of HCOOH=10−4;Kb= Molal elevation constant ph of 0.1 hcoo-

Answer 1

The pH of the 0.1 M HCOO⁻ solution is 8.5.

Answer 2

The formate ion (HCOO⁻) is a weak base. It undergoes hydrolysis in water to produce formic acid (HCOOH) and hydroxide ions (OH⁻). The equilibrium constant for this reaction is K_b. K_b for HCOO⁻ is calculated from the given K_a of HCOOH using $K_a \times K_b = K_w$. Setting up an ICE table for the hydrolysis reaction and using the K_b expression, we solve for the concentration of OH⁻ ions. Since K_b is small, we can use approximation. Once [OH⁻] is found, pOH is calculated using pOH = -log₁₀[OH⁻]. Finally, pH is calculated using pH + pOH = 14.