Question

5 g of Nacl is dissolved in 1000 g of water if the density of the resulting solution is 0.997 g per ml calculate the molality ,molarity , normality, & mole fraction of the solute assuming volume of solution is equal to that of solvent​

Answer 1

Answer:

molecular mass of NaCl=23*1+35.5*1

=58.5g/mol

molality=mass of solute*1000/molecular mass*mass of solvent(in g)

=5*1000/58.5*1000

.0854m

weight of solution=weight of solvent+weight of solute

=1000+5

=1005g

1 liter=1000ml=1cm cube

density=mass/volume

.997=1005/volume

volume=1005/.997

=1008.02 l

molarity=mass of solute in g/molecular mass*volume of solution in l

=5/58.5*1008.02

=5/58969.17

=8.479M

Explanation:

Answer 2

Given info : 5 g of Nacl is dissolved in 1000 g of water and the density of the resulting solution is 0.997 g/ml.

To find :

1. molality
2. molarity
3. normality
4. mole fraction

solution  : mass of solution = mass of solute + mass of solvent

here, mass of solute (NaCl)  = 5g

mass of solvent ( water ) = 1000g

now the mass of solution = 5g + 1000g = 1005g

∴ volume of solution = mass of solution/density of solution

= $\frac{1005g}{0.997g/ml}$ = 1008.024 ml

no of moles of solute = mass of solute/molar mass of solute

= $\frac{5g}{58.5g/mol}$ = 0.0855 mol

∴ molarity = no of moles of solutel/volume of solution in L

= $\frac{0.0855mol}{\frac{1008.024}{1000}L}$ = 0.0848 M

therefore the molarity of the solution is 0.0848M.

molality of the solution = no of moles of solute/mass of solvent in Kg

= $\frac{0.0855mol}{1 kg}$ = 0.0855 molal

therefore the molality of the solution is 0.0855molal.

normality of the solution = n - factor × molarity

here NaCl dissociates into Na⁺ and Cl⁻.

∴  n - factor = change in oxidation state of Na⁺/Cl⁻ = 1

now the normality of the solution = 1 × 0.0848 = 0.0848 N

no of moles of solvent( water) , n₁ = mass of water/molar mass of water

= $\frac{1000g}{18g/mol}$ = 55.5 mol

no of moles of solute (NaCl ) , n₂ = 0.0855 mol

∴ mole fraction of solute = $\frac{n_2}{n_1+n_2}$

= $\frac{0.0855}{55.5+0.0855}= 0.00154$

therefore the mole fraction of the solute is 0.00154