Question

The weight of the substance if it's molecular weight is 70 and in the gaseous form occupies 10litres at 27c and 700mm pressure

Answer 1

We can use the ideal gas Eqn.
Pv=nRT

here,
n=wb/mb

wb is weight of substance
mb is molecular weight.
R is universal gas constant
T is temp. in Kelvin

Now eqn. becomes

Wb= PVmb/RT

Substitute values of p,v,mb,R,T to get wb.

Hope you get your answer.

Answer 2

Given :-

Initially :

P1 = 700mm

T1=27°C + 273 = 300K

V1 =10 litres

Finally(stp) :

P2 = 760mm

T2 = 273k

To Find :-

V2 = ????

Using the gas equation that is,

=> P1V1 = P2V2

=> 700×10/300 = 760×V2/273

=> 273×60=760×V2×3

=> 16380 = 2280×V2

=> 16380/2280= V2

=> 7.18 litres = V2

Therefore:-

70g of gas X occupies 22.4litres at STP

? g of gas occupies 7.18 litres.

So:-

=> 22.4 litres = 70g

=> 1 litre = 70/22.4g

=> 7.18 litres = 7.18 × 70/22.4g =7.18g

Hence:-

V2 = 7.18 litres and

Weight of substance X is 22.45g.