Question:
1.06 g of Na$_2$CO$_3$ (molar mass = 106 g mol$^{-1}$) is dissolved in 500 g water. What is its molality?
1.06 g of Na$_2$CO$_3$ (molar mass = 106 g mol$^{-1}$) is dissolved in 500 g water. What is its molality?
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Always convert solvent mass to kg when calculating molality.
Updated On: Jan 6, 2026
- 0.2 m
- 0.02 m
- 2 m
- 0.04 m
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The Correct Option is B
Solution and Explanation
Molality $(m) = \dfrac{\text{moles of solute}}{\text{mass of solvent in kg}}$
Moles of Na$_2$CO$_3$ = $\dfrac{1.06}{106} = 0.01$ mol
Mass of water = 500 g = 0.5 kg
$m = \dfrac{0.01}{0.5} = 0.02$ mol/kg
Moles of Na$_2$CO$_3$ = $\dfrac{1.06}{106} = 0.01$ mol
Mass of water = 500 g = 0.5 kg
$m = \dfrac{0.01}{0.5} = 0.02$ mol/kg
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