Pressure of 1 g of an ideal gas A at 27 °C is found to be 2 bar
Pressure of 1 g of an ideal gas A at 27 °C is found to be 2 bar. When 2 g of another ideal gas B is introduced in the same flask at same temperature the pressure becomes 3 bar. Find a relationship between their molecular masses.
1 Answers
Mass of gas A , WA = 1g
Mass of gas B, WB = 2g
Pressure exerted by the gas A = 2 bar
Total pressure due to both the gases = 3 bar
In this case temperature & volume remain constant
Now if MA & MB are molar masses of the gases A & B respectively,therefore
pA V= WA RT/MA & Ptotal V = (WA/MA + WB/ MB) RT
= 2 X V = 1 X RT/MA & 3 X V = (1/MA + 2/MB)RT
From these two equations, we get
3/2 = (1/MA + 2/MB) / (1 /MA) = (MB + 2MA) / MB
This result in 2MA/ MB = (3/2) -1 = ½
OR MB = 4MA
Thus, a relationship between the molecular masses of A and B is given by
4MA = MB