Question

Calculate the molar mass of a gas

Answer 1

Answer:

MOLAR MASS = 32 g/mol

Explanation:

Condition of standard temperature and pressure(STP) are as follow:

Temperature = 273 K

Pressure = 1 atm (or 100000 Pa)

Here atm is atmosphere and Pa is Pascal

STP conditions arte used for measuring gas density and volume using Ideal Gas Law.Here 1 mole of ideal gas occupies 22.4 L of volume.

According toi Ideal Gas Equation :

PV = nRT

where P = pressure, n= number of moles, V = volume ,R= Ideal Gas Constant and T= temperature

$n=\frac{PV}{RT}$

From question:

V=280 ml = 0.28 L

P = 1 atm

R=0.08205 L atm/K mol

T=273 K

Putting values in above formula :

$n=\frac{1\times .280}{0.08205\times 273}$

n = 0.0125 moles

Now $n=\frac{given\ mass}{Molar\ mass}$

$Molar\ mass=\frac{given\ mass}{n}$

given mass = 0.4 g (given)

$Molar\ mass=\frac{0.4}{0.0125}$

On solving we get:

Molar mass = 32 g/mol