Question

87 cm3

of moist nitrogen is measured at 90C and 659 mm Hg pressure. Find the volume

of dry nitrogen at S.T.P. The vapour pressure of water at 90C is 9 mm Hg.​

Answer 1

Explanation:

Initial vol (V1) = 87 cc ;

V.P of water = 9 mm of Hg ;

Total pressure = 659 mm of Hg ;

Actual pressure (P1)

= total pressure - Vapour pressure

= (659 - 9) mm of Hg

= 650 mm og Hg ;

Initial temp (T1) = (273 + 9) K = 282 K ;

Final temp (T2) = 273 K ;

Let the final volume of N2 be V2

By combining Boyle's law and Charle's law, we get

P

1

V

1

T

1

=

P

2

V

2

T

2

or,

V

2

=

P

1

V

1

T

2

P

2

T

1

or,

V

2

=

650

×

87

×

273

760

×

282

or,

V

2

=

72.03

c

c

Hence, final volume is 72.03 cc