Question

how many moles of ar gas are present in a container with a volume of 78.4 l at stp?

Explanation:

Step1: Recall molar volume at STP

At STP, 1 mole of gas = 22.4 L

Step2: Calculate moles of Ar

Moles = Volume / Molar volume = $\frac{78.4\ \text{L}}{22.4\ \text{L/mol}}$

Step3: Compute the result

$\frac{78.4}{22.4} = 3.5$

Answer:

3.5