Question

A 4-g mass of NaOH is dissolved in 5mL of water.
what is the approximate molar concentration of the NaOH?

Answer 1

Molar mass NaOH = 40.0 g/mol

Volume in liters of solution :

5 mL / 1000 => 0.005 L 

number  of moles :

4 / 40 => 0.1 moles

M = n / V

M = 0.1 / 0.005

 = 20 mol/L or 20 M

hope this helps!