Question

A 20 gram monoatomic gas occupies 44.8 dm3 at STP what is the atomic mass weight of the gas

Answer 1

Given:

A 20-gram monoatomic gas occupies 44.8 dm³ at STP.

To find:

Atomic mass weight of the gas.

Solution:

According to standard temperature and pressure (STP),

temperature, T = 273.15K

pressure , P = 1 atm

volume , V = 22.4 L.

We know that,

PV = nRT,

where,

P = pressure

V = volume

n = amount of substance

R = ideal gas constant

T = temperature.

On substituting, we get:

• 1 atm × 22.4 L = n ×  0.082 atmL/mol/K × 273.15 K
• n = 22.4/(0.082 × 273.15) ≈ 1 mol

We know that,

Number of moles of a gas = given mass / atomic mass of gas.

We get,

• 20g/atomic mass of gas = 1 mol.

• The atomic mass of the gas = 20 g/mol.

The weight that occupies 22.4 dm³ at STP will be the atomic mass.

The atomic mass of the gas is 20gm/mol at 44.8 dm³. So, the atomic mass of the gas at 22.4 dm³ will be 10gm/mol.

Therefore, the atomic mass weight of the gas is 10gm/mol.