Question

70 gm solute is dissolved in 700 gm solvent to prepare a solution having density 1.5 g/ml. The ratio of its molality and molarity will be ______.

विकल्प

• 0.77

• 1.4

• 0.73

• 1.3

Answer 1

70 gm solute is dissolved in 700 gm solvent to prepare a solution having density 1.5 g/ml. The ratio of its molality and molarity will be 0.73.

Explanation:

Given: Solute mass (m₂) = 70 g

Solute mass (m₁) = 700 g

Density of solution (d) = 1.5 g/ml

molality (m) = `(m_2)/M_2 xx 1000/m_1`

= `70/M_2 xx 1000/700`

= `70/M_2 xx 10/7`

= `100/M_2`

Molarity (M) = `(m_2)/M_2 xx 1000/m_1`

V = `(m_1 + m_2)/d`

= `770/1.5`

= `70/M_2 xx 1000/(770/1.5)`

= `70/M_2 xx (1000 xx 1.5)/770`

Ratio of molality to molarity:

`m/M = (70/M_2 xx 1000/700)/(70/M_2 xx (1000 xx 1.5)/770)`

cancel `70/M_2`:

= `(1000/700)/(1500/770)`

= `770/(700 xx 1.5)`

= `770/1050`

= 0.73