Question

A mass of 1.37 g of an unknown gas is introduced into an evacuated 1.70 L flask If the pressure in the flask is 0.814 atm at 98 degrees C, which of the following gases might be in the flask?

a. CH4

b. C2H2

c. C2H6

d. C3H8

e. C4H10

Answer 1

Answer:

c. C₂H₆

Explanation:

Given data

mass: 1.37 g

volume: 1.70 L

pressure: 0.814 atm

temperature: 98°C + 273 = 371 K

We can find the molar mass of the gas using the ideal gas equation.

$P.V=n.R.T=\frac{m}{M} .R.T\\M=\frac{m.R.T}{P.V} =\frac{1.37g \times (0.08206atm.L/mol.K) \times 371K }{0.814atm \times 1.70L} =30.1g/mol$

C₂H₆ has a molar mass of about 30 g/mol and it could be the unknown gas.