Question

A sample contains 0.500 mol of aluminum. What is the mass of aluminum in the sample (in grams)?

Answer 1

13.5 g Al

Step-by-step explanation:

Recall that to go from moles to mass, you multiply the amount in moles by the molar mass of the substance.

0.500 mol Al
`((26.982 g Al)/(1 mol Al) )` = 13.491 g Al --> 13.5 g Al (3 sig figs)

Answer 2

`\boxed {\boxed {\sf About \ 13.5 \ grams \ of \ Al}}`

Step-by-step explanation:

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

• Aluminum (Al): 26.981538 g/mol

Use this number as a fraction.

`(26.981538 \ g \ Al )/(1 \ mol \ Al)`

Multiply by the given number of moles.

`0.500 \ mol \ Al *(26.981538 \ g \ Al )/(1 \ mol \ Al)`

The moles of aluminum will cancel.

`0.500 *(26.981538 \ g \ Al )/(1 )`

`0.500 *26.981538 \ g \ Al`

`13.490769 \ g \ Al`

The original number of moles, 0.500, has 3 significant figures, so our answer must have the same.

For the number we calculated, that is the tenth place. The 9 in the hundredth place tells us to round the 4 to a 5.

`13.5 \ g \ Al`

There are about 13.5 grams of aluminum in 0.500 moles.