GenChem pH problem

[tx3]

What is the pH of a solution with 0.5 mol of carbonic acid and 1.0 mol of bicarbonate dissolved in 2L?

If anyone could help me get started on this problem I would really appreciate it. The textbook explanation confuses me. Thank you!

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[hausee]

Do you have a pka of carbonic acid? If you do you can use pka to figure out H+ concentration because bicarbonate concentration already given.

 

[mehron]

Here's how I would do it:

H2CO3 + H2O <--> HCO3- + H+
I 0.25M 0.5M 0
C -x +x +x
E 0.25-x 0.5+x x

PKa pf H2CO3= (x+0.5)(x)/(0.25-x)

Find x

pH= -log [x]

 

[tx3]

pka = 10.24

 

[tx3]

thank you for your help

 

[zellyen]

PKa pf H2CO3= (x+0.5)(x)/(0.25-x)

dont you mean Ka or am i missing something