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physstudent1
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Homework Statement
A vessel contains 500mL of .1 molar H2S solution. For H2S Ka1 = 1 x 10^-7
Ka2 = 1.3 x 10^-13.
What will the pH be when 800mL of .1molar NaOH has been added.
Homework Equations
ph = -log([H])
ph = pka + log(B/A)
The Attempt at a Solution
This is how I started, I found the moles of each. I found I started with .08 moles of NaOH and .05 moles of H2S, subtracted them to get .03 moles of NaOH. Then .03 / (.5 + .8) to get the concentration (total volume), then because all that's left is strong base I took the -log(.023) and then subtracted that from 14 to get the pH. I keep ending up with 12.36 but the answer is 13.1. I need to be able to do this for my exam tomarrow, can anyone help?
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