Asked by Ethan

Calculate the concentration of H3O
+ present
in 0.377 M H2CO3.
Answer in units of mol/L

I know the Ka of H2CO3 is 4.3E-7. But I don't know what to do from there. (Or, I'm not getting the correct answer at least)
Answered by DrBob222
When you have problems like this post your work. That way we can see at a glance what is wrong.
Answered by Ethan
Well, I've tried going using 4.3e-7=x^2/0.377 to get to what x equals, I've been getting 0.0069, but it's incorrect.
Answered by Ethan
Once again I was foolish and mistyped an earlier answer, getting 4.02e-4 for my answer. I had not put in the 0 between the 4 and the 2 when submitting.
Answered by DrBob222
Your set up is ok. My answer is 4.026E-4M. However, you're allowed only two significant figures (set by the 4.3E-7 Ka value) so I would round that to 4.0E-4M. I suspect the s.f. thing is catching you.
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