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Question 12.19 (6th Edition)

Posted: Sat Dec 01, 2018 5:06 pm
by Leela_Mohan3L
The concentration of HCl is reduced to 12% of its initial value by dilution. By what amount does the pH of the solution change.

Re: Question 12.19 (6th Edition)

Posted: Sat Dec 01, 2018 6:40 pm
by armintaheri
Original concentration: 10x
Concentration diluted to 12% of original value: (10x)(0.12)
Original pH: -log(10x )
pH after dilution: -log((10x)(0.12)) = -log(10x) - log(0.12)

Change in pH = (Original pH) - (pH after dilution) = -log(10x) - (-log(10x) - log(0.12))
Change in pH = -log(10x) + log(10x) - log (0.12)
Change in pH = -log(10x) + log(10x) - log (0.12)
Change in pH = - log (0.12)
Change in pH = 0.92

As a shortcut, you could just remember that the change in pH is the negative log of the dilution percentage.