If 120 g of NaOH is dissolved in 2.5 L of water, what is the molarity of the solution?

1.2 M.

Explanation:

Molarity is the no. of moles of solute in a 1.0 L of the solution.

M = n/V.

M = (mass/molar mass) solute x (1000/V of the solution).

mass of NaOH = 120.0 g.

molar mass of NaOH = 40.0 g/mol.

V of the solution = 2.5 L = 2500.0 mL.

∴ M = (mass/molar mass) solute x (1000/V of the solution) = (120.0 g / 40.0 g/mol) x (1000 / 2500.0 mL) = 1.2 M.