Question

The molarity of a solution containing 8 g of NaOH (Molar mass = 40 g mol\(^{-1}\)) in 250 mL solution is:

• A. \(0.8 \, {M}\)
• B. \(0.4 \, {M}\)
• C. \(0.2 \, {M}\)
• D. \(0.5 \, {M}\)
• E. \(0.6 \, {M}\)

Hint:

To calculate molarity, always convert the volume of the solution into liters.

Answer 1

The Correct Option is A

Molarity (\(M\)) is given by the formula: \[ M = \frac{{moles of solute}}{{volume of solution in liters}} \] First, calculate the moles of NaOH: \[ {moles of NaOH} = \frac{{mass}}{{molar mass}} = \frac{8 \, {g}}{40 \, {g/mol}} = 0.2 \, {mol} \] Now, convert the volume of the solution from mL to L: \[ {Volume} = 250 \, {mL} = 0.25 \, {L} \] Thus, the molarity is: \[ M = \frac{0.2 \, {mol}}{0.25 \, {L}} = 0.8 \, {M} \]