Question

At 20° the solubility of N2 gas in water is 0.015g/L. When the partial pressure of the gas is 580 torr ,find the solubility of N2 in water at 20° c when partial pressure is 800torr



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Answer 1

Given :

At 20°C,

In case 1,

Solubility of Nitrogen gas in water = 0.015 g per litre.

Then, Partial pressure of gas = 580 torr.

In case 2,

Partial pressure of gas = 800 torr.

To find :

Solubility of Nitrogen gas in water.

Solution :

According to Henry's law, the partial pressure of dissolved gas into a liquid is directly proportional to the amount dissolved in liquid or the solubility of that material .

So,

$\\ \bf \: P \propto \: x \: \propto \: S$

Then

$\\ \bf \: \frac{P_1}{P_2} = \frac{ x_1}{ x_2} = \frac{ S_1}{ S_2}$

(equation 1)

where

P = Partial pressure of liquid

x = Mole fraction of liquid,

S = Solubility of liquid.

In this case also,

The partial pressure of liquid is increasing it means its solubility will also increase as stated in henry's law.

Putting the values of partial pressure, and solubility in equation 1,

we get

$\\ \bf \frac{580}{800} = \frac{0.015}{S_2}$

so,

Solubility of Nitrogen gas in second case :

$\\ \bf S_2 = 0.015 \times ( \frac{800}{580} )$

So,

The solubility of Nitrogen gas

in second case = 0.0207 g per litre