Formula for molarity is
Molarity=moles of solvent/solution in liters
In given data
NaOH is 21.2g which is needed to be convert in moles first
As no.of moles=mass in gram/molar mass
Molar mass of NaOH is 39.997g/mol
Putting in formula for mole.we get
No of mole = 21.2g/39.997gper mole
= 0.530mole
Now put these values in molarity equation, we get
Molarity =moles of NaOH/ solution in liter
= 0.530/7.92
=0.067M NaOH
