Question

If 80g of NaOH dissolve in 4L of solution. What is the concentration of NaOH in g/l​

Answer 1

Difficult ( actually impossible) question to answer with what is provided

But if you ask : What is the molarity of a solution when 80 g NaOH is dissolved in water to a final volume of 1.0L

Molar mass NaOH = 40 g/mol

80 g NaOH = 80 g/40 g / mol = 2 mol NaOH

Because volume of solution is 1.0 L

Molarity = 2 mol /L or 2 M