Question

Determine the identity of a sample of gas at STP conditions, with a mass of 120.00 grams that occupies 67.2 L.

a) N2
b) Ar
c) He
d) Ne
explain your answer

Answer 1

b) Ar

Step-by-step explanation:

Given data:

Mass of sample gas = 120.00 g

Volume of gas = 67.2 L

Identity of gas = ?

Solution:

We will calculate the molar mass do identify the sample:

Number of moles of gas:

PV = nRT

1 atm×67.2 L = n×0.0821 atm.L/mol.K×273 K

67.2 atm.L = n × 22.42atm.L/mol

n = 67.2 atm.L / 22.42atm.L/mol

n = 3 mol

Molar mass of gas:

Number of moles = mass/molar mass

Molar mass = 120.00 g/3 mol

Molar mass = 40 g/mol

The given sample of a gas is Ar.