Question

You have a partially filled party balloon with 2.00 g of helium gas. You then add 3.00 g of hydrogen gas to the balloon. Assuming constant temperature and pressure, determine how many times bigger the party balloon becomes with the addition of hydrogen.

Answer 1

Molar mass of He = 4.003 g/mol

mass(He)= 2.00 g

use:

number of mol of He,

n = mass of He/molar mass of He

=(2 g)/(4.003 g/mol)

= 0.4996 mol

Molar mass of H2 = 2.016 g/mol

mass(H2)= 3.00 g

use:

number of mol of H2,

n = mass of H2/molar mass of H2

=(3 g)/(2.016 g/mol)

= 1.488 mol

Initial number of mol,

ni = 0.4996 mol

final number of mol,

nf = 0.4996 mol + 1.488 mol

= 1.988 mol

Now use:

Vf/nf = Vi/ni

Vf/Vi = nf/ni

Vf/Vi = 1.988/0.4996

Vf/Vi = 3.98

Answer: 3.98 times