J.R. S. answered 03/10/21
Ph.D. University Professor with 10+ years Tutoring Experience
molality is defined as moles of solute per kg of solvent
moles of solute = 4.26 moles
kg of solvent = 345 g x 1 kg/1000 g = 0.345 kg
molality = 4.26 mol / 0.345 kg = 12.3 m