Question

What is the mass of 2.15 liters of N2 gas at STP?

Answer 1

Answer:

2.68g

Explanation:

Given parameters:

Volume of gas at STP = 2.15L

Unkown:

Mass of Nitrogen N₂ gas at STP = ?

Solution

To find the mass of the gas at STP, we use the mole concept approach.

In using the mole approach we follow the following procedures:

1. Find the number of moles of gas at STP using the relationship below:

                  Number of moles = $\frac{volume occupied}{22.4dm^{3} mol^{-1} }$

                         Note: 1L = 1dm³

2. Then using the mole and mass relationship, we can find the mass of the gas using the equation below:

                Mass = number of moles x molar mass

Workings

1.              Number of moles of N₂ = $\frac{2.15}{22.4}$

                Number of moles of N₂ = 0.096mole

2. Given that the atomic mass of N = 14g

                       Molar mass of N₂ = 2 x 14 = 28gmol⁻¹

Mass = 0.096mol x  28gmol⁻¹ = 2.68g