Explanation:
To convert from grams to moles we must use the molar mass, which is found on the Periodic Table.
Argon: 39.9 g/molUse the molar mass as a ratio.
Multiply by the given number of grams: 118
Flip the fraction so the grams of argon will cancel each other out.
The original measurement of grams had 3 significant figures, so our answer must have 3 sig figs.
For the number we calculated, that is the hundredth place. The 7 in the thousandth place tells us to round the 5 to a 6.
There are about 2.96 moles of Argon in 118 grams.