Question

A jar contains a gas and a few drops of water at T K. The pressure in the jar is 830 mm of Hg. The temperature of the jar is reduced by 1%. The vapour pressure of water at two temperatures are 30 and 25 mm of Hg. The new pressure in the jar is ______ mm of Hg.

विकल्प

• 456

• 675

• 817

• 1056

Answer 1

A jar contains a gas and a few drops of water at T K. The pressure in the jar is 830 mm of Hg. The temperature of the jar is reduced by 1%. The vapour pressure of water at two temperatures are 30 and 25 mm of Hg. The new pressure in the jar is 817 mm of Hg.

Explanation:

Here `"P"_(1"(gas)")` = 830 mm of Hg – 30 mm of Hg (gas) = 800 mm of Hg

P₂ = ?

T₁ = T K, T₂ = 0.99 T K

Then from P `∝` T (at const. V.)

`"P"_1/"P"_2 = "T"_1/"T"_2`

⇒ `800/"P"_2 = "T"/(0.99  "T")`

⇒ P₂ = 792 mm of Hg (of gas)

Net new pressure = 792 + 25 = 817 mm of Hg