Question

If the density of some lake water is $1.25g mL^{–1}$ and contains 92 g of $Na^+$ ions per kg of water, calculate the molality of $Na^+$ ions in the lake

Answer 1

Number of moles present in 92 g of $Na ^+$ ions $\frac{92g}{23g mol^{-1 }}$
= 4 mol
Therefore, molality of $Na ^+$ ions in the lake $= \frac{4 mol}{1kg}$
=4 m