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

Question

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

Philoid · Accepted Answer

Mass of ions = 92g

Molar mass of ions = Na⁺ = 23g(neglect the mass lost due to absence of a electron)

Moles of ions = mass of ions/molar mass

⇒ n = 92/23 moles

⇒ n = 4moles

Molality of solution = moles of solute/mass of solvent(in kg)

Molality = 4/1 = 4M

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