Questions are as follow, and answered one by one,
(1) What is step 1 in solving the problem?
Answer:
First of all moles of NaOH are calculated. This is done by applying following formula,
Moles = n = Mass / M.mass
(2) What is the molar mass of NaOH?
Answer:
Add all atomic masses of elements in NaOH to find the Molar mass.
Atomic Mass of Na = 22.98 g/mol
Atomic Mass of O = 16.00 g/mol
Atomic Mass of H = 1.008 g/mol
_______________
Molar Mass of NaOH = 39.988 g/mol
(3) What is the Molarity of this solution?
Answer:
Molarity = Moles / Vol
∴ Moles = 40g / 39.988g/mol = 1.0 mol
So,
Molarity = 1.0 mol / 6.0 L
Molarity = 0.16 mol.L⁻¹
