Question

Since helium is lighter than air, it is difficult to measure the mass of a sample, so to find out the mass of helium in a birthday balloon, a student transferred the helium to a fixed 1.50 L vessel at 25.0 °C and found the pressure to be 3.04 atm. What mass of helium is in the balloon?

Answer 1

Answer:

0.7457 g is the mass of the helium gas.

Explanation:

Given:  

Pressure = 3.04 atm

Temperature = 25.0 °C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15  

So,  

T₁ = (25.0 + 273.15) K = 298.15 K  

Volume = 1.50 L

Using ideal gas equation as:

$PV=nRT$

where,  

P is the pressure

V is the volume

n is the number of moles

T is the temperature  

R is Gas constant having value = 0.0821 L.atm/K.mol

Applying the equation as:

3.04 atm × 1.50 L = n × 0.0821 L.atm/K.mol × 298.15 K  

⇒n = 0.1863 moles

Molar mass of helium = 4.0026 g/mol

The formula for the calculation of moles is shown below:

$moles = \frac{Mass\ taken}{Molar\ mass}$

Thus,

$0.1863\ mole= \frac{Mass}{4.0026\ g/mol}$

$Mass_{He}= 0.7457\ g$

0.7457 g is the mass of the helium gas.