Question

Calculate the molarity of a solution containing 5g of NaOH in 450 mL solution .

• A. \(0.278 \times 10^{-3} M \)
• B. \(0.278\ M\)
• C. \(2.78 \times 10^{-3} M\)
• D. \(2.78\ M\)

Answer 1

The Correct Option is B

To calculate the molarity of a solution, we need to determine the number of moles of solute and divide it by the volume of the solution in liters.
Given:
Mass of NaOH = \(5\ g\)
Volume of solution = 450 mL = \(0.450\  L\)
First, we need to calculate the number of moles of NaOH. The molar mass of NaOH is approximately 40 g/mol (\(22.99\  g/mol\) for Na + \(16.00 \ g/mol\) for O + \(1.01\ g/mol\) for H).
Number of moles of NaOH = \(\frac {\text {Mass of NaOH}}{\text {Molar mass of NaOH}}\) = \(\frac {5\ g }{40\ g/mol}\)= \(0.125\ mol\)
Now we can calculate the molarity of the solution using the formula:
Molarity \((M) =\frac {\text {Moles of solute}}{\text {Volume of solution (in liters)}}\)

Molarity \((M) = \frac {0.125\ mol }{0.450\ L} ≈ 0.278\ M\)

Therefore, the molarity of the solution containing \(5\ g\) of NaOH in \(450\ mL\) solution is approximately \(0.278 \ M\).

Answer 2

Moles of NaOH= $\frac{5}{40\,gmol^{-1}} $ = 0.125 mol

Volume of the solution in litres = 450 mL = \(0.450\  L\)

Molarity \((M) =\frac {\text {Moles of solute}}{\text {Volume of solution (in liters)}}\)

Molarity \((M) = \frac {0.125\ mol }{0.450\ L} ≈ 0.278\ M\)

Hence, the molarity of the solution containing \(5\ g\) of NaOH in \(450\ mL\) solution is approximately \(0.278 \ M\).