High School

Example 4: Liters to Moles

How many moles are present in 6.2 L of [tex]$H_2$[/tex] at STP?

Answer :

To find out how many moles of [tex]\( H_2 \)[/tex] gas are present in 6.2 liters at standard temperature and pressure (STP), you can follow these steps:

1. Understand STP conditions: At standard temperature and pressure (STP), one mole of any ideal gas occupies 22.4 liters. This is a known value often used in gas law calculations.

2. Use the molar volume: We can use the relation of volume and moles at STP to find our answer. You have the volume of the gas (6.2 liters), and you need to find out how many moles this corresponds to.

3. Calculate the moles: Use the formula:
[tex]\[
\text{Number of moles} = \frac{\text{Volume of gas at STP}}{\text{Molar volume at STP}}
\][/tex]
Substitute the known values into the formula:
[tex]\[
\text{Number of moles} = \frac{6.2 \text{ L}}{22.4 \text{ L/mol}}
\][/tex]

4. Solve the calculation:
When you divide 6.2 by 22.4, you get approximately 0.28 moles.

Therefore, there are about 0.28 moles of [tex]\( H_2 \)[/tex] gas present in 6.2 liters at STP.