To find the number of moles in 15.0 grams of argon, we need to use the formula:
Number of moles = Mass (g) / Molar mass (g/mol)
The molar mass of argon (Ar) is approximately 39.95 g/mol. Now, we can plug in the values:
Number of moles = 15.0 g / 39.95 g/mol ≈ 0.375 moles
So, there are approximately 0.375 moles of argon in 15.0 grams. This calculation is useful in chemistry for converting between grams and moles, which helps in understanding the amount of substance in a chemical reaction.