A solution of HCOOH has 0.16M HCOOH at equilibrium. The Ka for HCOOH is 1.8×10−4. What is the pH of this solution at equilibrium? Express the pH numerically.

Question

asked Apr 17, 2021 106k views

1 Answer

Lejlek · Answer 1 · 2021-04-24T11:32:37+0000

Answer:

pH=2.28

Step-by-step explanation:

Hello,

In this case, for the acid dissociation of formic acid (HCOOH) we have:

$HCOOH(aq)\rightarrow H^+(aq)+HCOO^-(aq)$

Whose equilibrium expression is:

Ka=([H^+][HCOO^-])/([HCOOH])

That in terms of the reaction extent is:

1.8x10^(-4)=(x*x)/(0.16-x)

Thus, solving for
which is also equal to the concentration of hydrogen ions we obtain:

x=0.00528M

[H^+]=0.00528M

Then, as the pH is computed as:

pH=-log([H^+])

The pH turns out:

$pH=-log(0.00528M)\\\\pH=2.28$

Regards.