Question

The density of 'x' M solution ('x' molar) of NaOH is \(1.12 \, \text{g/mL}\). While in molality, the concentration of the solution is \(3 \, \text{m}\) (3 molal). Then x is:
Given: Molar mass of NaOH is \(40 \, \text{g/mol}\)

• A. 3.5
• B. 3
• C. 3.8
• D. 2.8

Answer 1

The Correct Option is B

We know the relationship between molality and molarity:
\[\text{Molality} = \frac{1000 \times M}{1000 \times d - M \times (\text{Molar mass of solute})}\]
Substituting the values:
\[3 = \frac{1000 \times x}{1000 \times 1.12 - x \times 40}\]
Rearranging:
\[3 \times (1000 \times 1.12 - x \times 40) = 1000 \times x\]
Simplify:
\[3 \times 1120 - 120x = 1000x\]
\[3360 = 1120x\]
Solving:
\[x = 3\]
Thus, the molarity of the solution is 3.0 M.