Question

to make a saturated solution 36g of sodium chloride is dissolved in 100g of water at 293K. Find its concentration at this temperature

Answer 1

Molecular mass of NaCl(solute) = 58.5gm/mol

Given mass of NaCl = 36gm

Therefore moles of NaCl = 36/58.5 = 0.615 moles

Weight of water(solvent) in kg = 0.1kg

Molality = (moles of solute)/(moles of solvent) = (0.615/.1) = 6.15 moles/kg

This was concentration of solute in molality

Now, mass of solution = 36+100 = 136gm

Now concentration of the solution =

(Weight of solute)/(Weight of solution) * 100%

= (36*100)/(136) = 26.47% (w/w)

This was the concentration of the solution expressed in weight upon weight

Hope it helps :)