Question

A sample containing 2.00 moles of Ne gas has an initial volume of 9.00 L . What is the final volume of the gas, in liters, when each of the following changes occurs in the quantity of the gas at constant pressure and temperature?

A. A leak allows one-half of the Ne atoms to escape.

B. A sample of 3.30 moles of Ne is added to the 2.00 moles of Ne gas in the container.

C. A sample of 15.0 g of Ne is added to the 2.00 moles of Ne gas in the container.

Answer 1

A)

Given:

Vi = 9.00 L

ni = 2.00 mol

nf = 1.00 mol

use:

Vi/ni = Vf/nf

9.00 L / 2.00 mol = Vf / 1.00 mol

Vf = 4.50 L

Answer: 4.50 L

B)

Given:

Vi = 9.00 L

ni = 2.00 mol

nf = 3.30 mol + 2.00 mol = 5.30 mol

use:

Vi/ni = Vf/nf

9.00 L / 2.00 mol = Vf / 5.30 mol

Vf = 23.85 L

Answer: 23.8 L

C)

Molar mass of Ne = 20.18 g/mol

mass(Ne)= 15.0 g

use:

number of mol of Ne,

n = mass of Ne/molar mass of Ne

=(15 g)/(20.18 g/mol)

= 0.7433 mol

Given:

Vi = 9.00 L

ni = 2.00 mol

nf = 2.00 mol + 0.7433 mol = 2.7433 mol

use:

Vi/ni = Vf/nf

9.00 L / 2.00 mol = Vf / 2.7433 mol

Vf = 12.3 L

Answer: 12.3 L