Question

calculate the pHof 0.01 M HF acid.

Answer 1

Answer - We are given,

[HF] = 0.010 M

We are given the concentration of weak acid, HF and asked for the pH of the solution. To determine the pH of the solution the steps are involved as follow,

Step 1) The Concentration of Hydronium ion ([H3O+])

    The ICE chart for the HF is,

	HF	H2O	H3O+	F-
I	0.01		0	0
C	-x		+x	+x
E	0.01-x		+x	+x

The Ka value for HF is 6.6 x 10-4.

The Ka expression for HF is,

  
  

  

By rearranging the above equation in terms of the quadratic equation

The quadratic formula is,

  

By plugging the values of a = 1, b = 0.00066, and c = - 6.6 x 10-6 in quadratic formula to solve x value.

  

At equilbirum , x = [H3O+] = 0.00226 M

Step 2) The pH of the Solution :

The formula for pH is

pH = -log [H3O+]

       = -log 0.00226 M

         = 2.64

Therefore, the pH of 0.01 M HF acid is 2.64.