Calculate the number of moles of methanol in 5 L of its solution, if the density of solution is 0.981 kg `L^(-1)` (Molar mass of methanol = 32.0 g `"mol"^(-1)`).

Explanation

We are given that
Density (d) = 0.981 `"kg L"^(-1)`
Volume (V) = 5 L
Molality (m) = 2 m
We are to find the number of methanol
Using the relation `d="Mass"/("Volume")`
`"mass"=d xxV=0.981xx5=4.91kg`
Now, we know that
`"Molality (m)"=("Number of moles of solute")/("Weight of solvent in kg"),2=("Number of moles of solute")/(4.91)`
`rArr"number of moles of solute"=2xx4.91=9.82mol`.