A weak acid solution, HX 0.37 M, has a pH of 3.70. Calculate the acidity constant for this acid.

Answer 1

pH = -log(H^+)
3.70 = -log(H^+)
Convert that; I get about 2E=4 but you need to confirm that.
...........HX ==> H^+ + X^-
I.........0.37....0......0
C........-2E-4...2E-4...2E-4
E......0.37-2E-4..2E-4...2E-4

Substitute into the Ka expression and solve for Ka.