Question

if 4 g of NaOH is dissolve in 10ml of water and
form the solut. Find out mole fract of NaOH and H2O.
​

Answer 1

Explanation:

Mass of NaOH=4 g

Number of moles of NaOH=40g / 4 g = 0.1 mol

Mass of H²O=36 g

Number of moles of H²O= 36 g / 18 g = 2 mol

Mole fraction of water = Number of moles of H²O / No. of moles of water+No. of moles of NaOH

= 2 / 2+0.1 = 2/2.1

= 0.95

Mole fraction of NaOH = Number of moles of NaOH / No. of moles of NaOH+No. of moles of water = 0.1 / 2+0.1

= 0.1 / 2.1 = 0.047

Mass of solution = mass of water + mass of NaOH=36g+4 g=40 g

Volume of solution =40×1=40 mL.

( Since specific gravity of solution is =1 g mL -¹)

Molarity of solution =

Number of moles of solut / Volume of solution in litre = 0.1 mol NaOH / 0.04L

=2.5 M

Answer 2

mole fraction of water and NaOH is 0.846 and 0.153 respectively

Explanation:

Given:

mass of NaOH = 4 g

V = 10 ml = 10 g of water

moles of NaOH = 4/40 = 0.1 mol

mass of H₂O = 10 g

moles of H₂O = 10/18 = 0.55 mol

We know that,

Mole fraction

For H₂O =  no. of moles of H₂O/ no. of moles of H₂O + no. of moles of NaOH

              = 0.55/0/0.55 + 0.1

              = 0.846

For NaOH = 0.1/0.65  

                  = 0.153