What is the pH of the solution formed...?

Question

100ml of HCl acid of pH 4.0 is mixed with 100mL of HCl acid of pH 5.0. What is the pH of the solution formed?

Answer 1

Use amount = volume x concentration.

You have (0.1L x 10^-4 M) + (0.1L x 10^-5M) H+ in 200 mL.

So find total amount of H+, divide by 0.2L to get [H+], and use definition of pH.

Answer 2

well M = mmol H+/mL   the total mmoles of H+=

mmoles =  100( 0.0001M )  + 100( 0.00001M )= 0.01 + 0.001

= 0.011mmoles of H+  in 100 + 100 mL

pH 4 = 0.0001 M in H+   pH 5 = 0.00001 M in H+

0.011 mmole/200 mL = 5.5 X 10^-5 M in H+

pH = -log [H+ ] = -log ( 5.5 X 10^-5 moles/liter H+ )

pH = 5 - log 5.5 = 4.26 The pH is 4.26