Question

The volume of a 4.3 gram gaseous sample is 3.93 litre at 25 °C temperature and 770mm pressure . What will be the weight of 2 litre of this gas at STP?​

Answer 1

Given - Initial weight - 4.3 gram

Initial volume - 3.93 litre

Initial temperature - 25°  C - 298 K

Initial pressure - 770 mm

Final volume - 2 litre

STP conditions -

Final Temperature - 273 K

Final pressure - 760 mm

Find - Weight of 2 litre of given gas.

Solution - Using ideal gas law equation to find the weight of gas in question. The ideal gas law equation is PV = nRT. n can be further represented as weight/molecular weight.

Therefore, the two conditions can be related as P1V1/w1T1 = P2V2/w2T2.

Keeping the values in equation-

770*3.93/(4.3*298) = 760*2/(w2*273)

w2*273 = (760*2)*(4.3*298)/(770*3.93)

w2*273 = 643.6

w2 = 2.35 gram.

Hence, the weight of given gas at STP is 2.35 gram.