3.25 kg in g = 3.25 * 1000 = 3250 g
Molar mass C₂H₆O₂ = 62.0 g/mol
Mass solvent = 7.75 kg
Number of moles:
n = mass solute / molar mass
n = 3250 / 62.0
n = 52.419 moles
Molality = moles of solute / kilograms of solvent
M = 52.419 / 7.75
M = 6.7637 mol/kg
hope this helps!
