Concentrated sodium hydroxide is 505 by mass and has a densi

Concentrated sodium hydroxide is 50.5% by mass and has a density of 1.53 g/mL. What is the pH of concentrated sodium hydroxide? NaOH FW=40.0 g/mol Please show work!

a) -1.30

b) 12.29

c)15.29

d)15.58

e) 13.95

I know the answer is C, I just don\'t know how to solve it

Solution

Concentrated sodium hydroxide is 50.5% by mass

Mass of sodium hydroxide = 50.5 gm

moles of NaOH = (50.5/40) = 1.26 moles

mass of solution = 100 gms

volume of sultion = mass/ density = 100/1.53 = 65.36 ml = 65.36 x 10^-3 L

conc oh OH- ion = moles / volume = 1.26/(65.36 x 10^-3) = 0.019 x 10^3 moles/L

pOH = - log[OH-] = - log[0.019 x 10^3] = -1.29

pH = 14- pOH = 14-(-1.29) = 15.29