Question

A balloon has a volume of 1.34 liters with 2.00 moles of helium gas. How many moles of helium gas must be added to get the volume to 7.00 liters.

Answer 1

Avogadro's law

`( V1)/(V2) = (n1)/(n2) \\ (1.34)/(7) = (2)/(x) \\ x = (7 * 2)/(1.34) \\ x = 10 \: mol`

Answer 2

8.4 mol.

Explanation:

The pressure and temperature are constant. The only variables are the volume and number of moles, so we can use Avogadro’s Law:

The volume of a gas is directly proportional to the number of moles.

V = kn

or

V₂/V₁ = n₂/n₁ Multiply both sides by n₁ and transpose

n₂ = n₁ × V₂/V₁

n₁ = 2.00 mol; V₁ = 1.34 L

n₂ = ? mol; V₂ = 7.00 L Solve for V₂

n₂ = 2.00 × 7.00/1.34

n₂ = 2.00 × 5.223

n₂ = 10.4 mol

===============

The balloon originally held 2.00 mol of helium. It now holds 10.4 mol.

Moles added = 10.4 – 2.00

Moles added = 8.4 mol