3.63 m (molal) aqueous solution means that 3.63 moles of particular solute is dissolved in 1 Kg (1000 g) of water (solvent).
So,
The concentration of Solute = 3.63 moles
Moles of water are calculated by using following formula,
Moles = mass / M.mass
mass of water = 1000g
M.mass of water = 18.01 g/mol
Putting the values,
Moles = 1000 g / 18.01 g/mol
Moles = 55.524 mol
Now, having both, moles of solute and moles of solvent we can calculate mole fraction by applying following formula,
Mole Fraction = Moles of Solute ÷ ( moles of solute + moles of solvent)
Putting values,
Mole Fraction = 3.63 mol ÷ (3.63 mol + 55.524 mol)
Mole Fraction = 3.63 mol ÷ 59.154 mol
Mole Fraction = 0.0614
