A 0.200*g0.200g mass of sodium hydroxide is dissolved in a 0.500*L0.500L volume of water? What are pOHpOH, and pHpH of this solution?

1 Answer
Jan 4, 2017

pH=14-pOHpH=14pOH

Explanation:

[HO^-]="Moles of hydroxide"/"Volume of solution"[HO]=Moles of hydroxideVolume of solution

=((0.2*g)/(40.00*g*mol^-1))/(0.500*L)=0.01*mol*L^-1=0.2g40.00gmol10.500L=0.01molL1.

We (reasonably) assume no volume change on dissolution. Some heat will be evolved. Why?

pOH=-log_10[HO^-]=-log_10(10^-2)=-(-2)=2pOH=log10[HO]=log10(102)=(2)=2.

But we know for a fact that pH+pOH=14pH+pOH=14

And thus pH=............?