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6B 1

Posted: Wed Dec 04, 2019 6:12 pm
by rachelle1K
The question asks for change in pH when HCL concentration is reduced by 12%. I saw a previous chem community post where they plugged in -log(.12) to find the answer, but why don't we plug in H+ (pH= -log([.88])) since it is asking for the value of the change?

Re: 6B 1

Posted: Thu Dec 05, 2019 3:40 pm
by Indy Bui 1l
I believe the question says it is reduced TO 12% of its total, not reduced by 12%.

You would use -Log[0.12] and compared to Log(1), which is 0 the difference is just the value of -Log[0.12]

Re: 6B 1

Posted: Thu Dec 05, 2019 3:52 pm
by Justin Vayakone 1C
Doing log[.88] means the concentration was reduced by 12%, but the problem is asking for when it decreases to 12%.

The equation for the initial pH is:
Final pH:
To find the change, just do final pH - initial pH. Through some algebra, you should get which equals 0.92.