Question

Measured mass NaCl- 11.690g
Measured volume of water - 100.0mL
molar mass of NaCl= 58.44g/mol
0.2mol NaCl
Total moles of all solutes including cation and anion = 0.4 mol

Determine the mass (in kg) of solvent (assume that the density of water is 1.000g/mL).

Determine the molality (in m or mol/kg) of all solutes.

Answer 1

mass of water in g

density of water = 1.000 g/mL

mass = volume x density

mass = 1.000 g/mL x 100.0 mL = 100 g

mass in kg = 0.1 kg

total mass of 0.4 moles solute (NaCl)= 0.4 moles x 58.44 g/mol = 23.376 g = 0.023376 kg

molality = no. of moles / mass in kg

molality = 0.4 moles / 0.1 kg = 4 m

measured mole of NaCl is 0.2 mole so molarity of it is = 0.2 mole / 0.1 kg = 2 m

if we total (0.4 mol + 0.2 mol) = 0.6 mol than molarity will be

molarity = 0.6 mol/0.1 kg = 6 m