Question

find the relative molecular mass of a gas ,0.546 gram of which occupies 360 cc at 87 degree Celsius and 380 mm HG pressure

Answer 1

P1 = 380 mm P2 = 760mm

P1V1/T1 = P2V2/T2

V1= 360 cc    V2 = X cc 

so, V2 = P1V1T2/T1P2 = 380 x 360 x 273/360 x 760 = 136.5 cc

T1 = 87 +273 K 

T2 = 273 K

 

So, 136.5 cc of the gas at STP weighs = 0.546 g

Therefore, 1000 cc of the gas at STP weighs = 0.564/136.5    x 1000 = 4 g

 

We know Vapour density = wt of 1000 ml gas/wt of 1000 ml of H2 = 4/0.09 = 44.44

 

Relative molecular mass or mw of gas = 2 x VD = 2 x 44.44  =  88.88 g

 

Answer 2

Answer:89.5 amu

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