Question

Part A

Calculate the density of oxygen, O2, under each of the following conditions:

STP

1.00 atm and 35.0  ∘C

Express your answers numerically in grams per liter.

Part B

To identify a diatomic gas (X2), a researcher carried out the following experiment: She weighed an empty 3.6-L bulb, then filled it with the gas at 2.00 atm and 23.0  ∘C and weighed it again. The difference in mass was 8.3 g . Identify the gas.

Express your answer as a chemical formula.

Answer 1

A)

i)

P = 1.0atm

T = 273 K

Molar mass of O2 = 32 g/mol

Lets derive the equation to be used

use:

p*V=n*R*T

p*V=(mass/molar mass)*R*T

p*molar mass=(mass/V)*R*T

p*molar mass=density*R*T

Put Values:

1.0 atm *32.0 g/mol = density * 0.08206 atm.L/mol.K *273.0 K

density = 1.4284 g/L

Answer: 1.43 g/L

ii)

P = 1.0atm

T= 35.0 oC

= (35.0+273) K

= 308 K

Molar mass of O2 = 32 g/mol

Lets derive the equation to be used

use:

p*V=n*R*T

p*V=(mass/molar mass)*R*T

p*molar mass=(mass/V)*R*T

p*molar mass=density*R*T

Put Values:

1.0 atm *32.0 g/mol = density * 0.08206 atm.L/mol.K *308.0 K

density = 1.2661 g/L

Answer: 1.27 g/L

B)

Given:

P = 2.0 atm

V = 3.6 L

T = 23.0 oC

= (23.0+273) K

= 296 K

find number of moles using:

P * V = n*R*T

2 atm * 3.6 L = n * 0.08206 atm.L/mol.K * 296 K

n = 0.2964 mol

mass(solute)= 8.3 g

use:

number of mol = mass / molar mass

0.2964 mol = (8.3 g)/molar mass

molar mass = 28 g/mol

This is molar mass of N2 gas

Answer: N2