The density of lake water is 1.3 g/cc. and it contains 69 g of $N a^{+}$ ions per kg of water. What is molality of $N a^{+}$ ion in the lake?

1 m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

3 m

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

2 m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

4 m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is A 3 m
Lake water contains $69$ $g$ of $N a^{+}$ per $k g$ of water.

$∴$ moles of $N a^{+} = \frac{weight}{molecular weight} = \frac{69}{23} = 3$ moles

Mass of solvent (water) $= 1000 - 69 = 931$ $g$

$Molality (M) = \frac{Moles of solute}{Mass of solvent (g)} \times 1000$

$⟹ M = \frac{3}{931} \times 1000$

$⟹ M = 3.22$ $m$

$⟹ M \approx 3$ $m$

Hence, the correct option is $B$

Suggest Corrections

Similar questions

If the density of some lake water is 1.25 g mL⁻¹ and contains 92 g of Na⁺ ions per kg of water, calculate the molality of Na⁺ ions in the lake.

If the density of some lake water is $1.25 g m L^{- 1}$ and contains 92 g of $N a^{+}$ ions per kg of water, calculate the molarity of $N a^{+}$ ions in the lake.

Q. If the density of water of a lake is

1.25

m L^{- 1}

and one kg of lake water contains

92

g of

N a^{+}

ions. Calculate the molarity of

N a^{+}

ions in this lake water.
(At. mass of

N a

= 23

m o l^{- 1}

Q. A solution of sodium sulphate contains

92

g of

N a^{+} i o n s

per kilogram of water. The molality of the

N a^{+}

ions in the solution in mol

k g^{- 1}

is:

Q. A solution of sodium sulfate contains 92 g of

N a^{+}

ions per kilogram of water. The molality of

N a^{+}

ions in that solution in

m o l k g^{- 1}

is:

Join BYJU'S Learning Program

The density of lake water is 1.3 g/cc. and it contains 69 g of Na+ ions per kg of water. What is molality of Na+ ion in the lake?

The correct option is A 3 mLake water contains 69 g of Na+ per kg of water.∴ moles of Na+=weightmolecular weight=6923=3 molesMass of solvent (water)=1000−69=931 gMolality (M)=Moles of soluteMass of solvent (g)×1000⟹M=3931×1000⟹M=3.22 m⟹M≈3 mHence, the correct option is B

The density of lake water is 1.3 g/cc. and it contains 69 g of $N a^{+}$ ions per kg of water. What is molality of $N a^{+}$ ion in the lake?