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Chemistry
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Calculate [OH-] of a 7.00×10-3 M aqueous solution of ethylamine (C2H5NH2Kb = 5.60×10-4).

Calculate the pH of the above solution.

Feb 15th, 2015

C2H5NH2+H2O===C2H5NH3+ +OH-

So Kb=[C2H5NH3+][OH-]/[C2H5NH2]

Assuming the final concentration of OH- is x

Then Kb=x^2/(7.00×10^-3-x)=5.60×10^-4

                  x^2=5.60×10^-4(7.00×10^-3-x)

              x^2+5.60×10^-4x-39.2×10^-7=0

                        x=0.00172

So [OH-]=0.00172 M

pH=14-(-log [OH-])=11.2

Feb 15th, 2015

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