Question

HCOOH(aq) <-----> H^+ (aq)+ HCOO^-(aq)

The equilibrium constant (Ka) for Reaction 3 at 25 °C is 1.80 × 10−4 mol dm−3. Calculate the equilibrium concentration of hydrogen ions if the concentration of formic acid at equilibrium is 0.00500 mol dm−3

Answer 1

I don't know what reaction 3 is.

........HCOOH ==> H^+ + HCOO^-
I.......0.005.....0.......0
C.......-x........x.......x
E......0.005-x....x.......x

Substitute the E line into the Ka expression and solve for x = H^+.

Answer 2

Sorry I should have left that out, it's just the formula
HCOOH(aq) <-----> H^+ (aq)+ HCOO^-(aq)

Answer 3

The solution I posted stands.

Answer 4

OK thanks....
In the question, and in the example in the textbook there was no example of using an ICE table. Tables make assigning values so much easier

Answer 5

ICE tables are the baling wire of chemistry.