Moles, Molar Mass, and Molarity│Please Help!

Question

What is the molarity of a solution that contains 50.0g of NaOH (molar mass = 40 grams/mole) in 2.0L of solution?

1. 25M
2. 2.5M
3. 1.3M
4. 0.63M

Answer 1

Molarity = moles of solute/volume of solution.

Moles of NaOH = mass/molar mass = 50g/(40g/mol) = 1.25mol NaOH

Molarity = 1.25mol/2.0L = 0.625M = 0.63M

So the answer is 0.63M