Question

3.2 g of a gas at occupy the same volume as 0.6266 g of CH4 at 17°C at constant pressure
Find the molecular mass of the gas.​

Answer 1

Assuming gas temperature = 25, 3.2 g of a gas at 25°C occupy the same volume as 0.6266 g of CH4 at 17°C at constant pressure

The molecular mass of the gas : 842.1 g/mol

Find the molecular mass of the gas.​

Further explanation

Given

3.2 g of gas

0.6266 g of CH4

Required

the molecular mass of the gas

Solution

Because V, P, and R are the same, from ideal gas law :

PV=nRT

n₁T₁=n₂T₂

n₂=moles CH₄= 0.6266 : 16 g/mol = 0.0392

T₁=25+273=298 K

T₂=17+273=290 K

mol of gas :

$\tt n_1=\dfrac{n_2.T_2}{T_1}=\dfrac{0.0392\times 290}{298}=0.038$

molecular mass :

$\tt M=\dfrac{3.2}{0.038}=842.1$