What is the molal concentration of a solution made by dissolving 34.2 g of sucrose, c12h22o11 (molar mass 342.34 g/mol), in 125 g of water?

Molality is the number of moles of solute in 1 kg of solvent

number of moles of sucrose - mass of sucrose / molar mass

number of moles of sucrose - 34.2 g / 342.34 g/mol = 0.0999 mol

number of moles in 125 g of water - 0.0999 mol

therefore number of moles in 1000 g - 0.0999 / 125 x 1000 = 0.799 mol/kg

molality of sucrose solution - 0.799 mol/kg