Question #31148

1 Answer
Feb 2, 2017

The given NaOH solution is 5%w/w

This means 100g solution contains 5g NaOH and 95g water.

The density of solution is not known. So the volume of solution can not be found out.

If we assume that the solution being dilute the volume of solution is approximately equal to the volume of solvent water, then we can proceed to calculate the pH of the solution. Taking density of water 1g"/cc" the volume of water as well as solution will be 95cm^3=95xx10^-3L

The amount of NaOH in solution

=5g=(5g)/(40g"/mol")=1/8=0.125mol

So the concentrantion of NaOH
=0.125/(95xx10^-3)M=25/19M

So the concentration of OH^"-"=25/19M

So pH=pK_w-pOH

=14-log_10=14-log_10[OH^"-"]

=14-log_10(25/19)=13.88