Question

2g NaCl is dissolve in 200g water if freezing point of solution is -1.2°C . calculate amount of ice separated.kf= 1.86​
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Answer 1

Given:

Mass of NaCl, w = 2 gm

Total mass of water = 200 gm

Freezing point of solution = -1.2°C

Kf = 1.86

To Find:

Amount of ice separated.

Calculation:

- Freezing point of water = 0°C

- Depression in freezing point, ΔTf = 0 - (-1.2) = 1.2

- We know that:

Depression in freezing point, ΔTf = Kf × m

⇒ ΔTf = Kf × (w × 1000)/(M.wt × W)

⇒ 1.2 = 1.86 × (2 × 1000)/(58.5 × W)

⇒ W = (1.86 × 2 × 1000)/(1.2 × 58.5)

⇒ W = 3720/70.2

⇒ W = 52.99 gm

- Amount of ice separated = 200 - 52.99 = 147.01 gm

- So 147.01 gm of ice is separated out.