Question

How many moles is 118 grams of Argon

Answer 1

`\boxed {\boxed {\sf About \ 2.96 \ moles \ of \ Argon}}`

Step-by-step explanation:

To convert from grams to moles we must use the molar mass, which is found on the Periodic Table.

• Argon: 39.9 g/mol

Use the molar mass as a ratio.

`(39.9 \ g \ Ar)/(1 \ mol \ Ar)`

Multiply by the given number of grams: 118

`118 \ g \ Ar *(39.9 \ g \ Ar)/(1 \ mol \ Ar)`

Flip the fraction so the grams of argon will cancel each other out.

`118 \ g\ Ar * (1 \ mol \ Ar)/(39.9 \ g \ Ar)`

`118 * ( 1 \ mol \ Ar)/(39.9 \ g \ Ar)`

`\frac {118 \ mol \ Ar }{ 39.9 }`

`2.95739348 \ mol \ Ar`

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.

`2.96 \ mol \ Ar`

There are about 2.96 moles of Argon in 118 grams.