Question

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

Answer 1

Answer:

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

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.

$\frac{26.981538 \ g \ Al }{1 \ mol \ Al}$

Multiply by the given number of moles.

$0.500 \ mol \ Al *\frac{26.981538 \ g \ Al }{1 \ mol \ Al}$

The moles of aluminum will cancel.

$0.500 *\frac{26.981538 \ g \ Al }{1 }$

$0.500 *26.981538 \ g \ Al$

$13.490769 \ g \ Al$

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.

Answer 2

Answer:

13.5 g Al

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 $(\frac{26.982 g Al}{1 mol Al} )$ = 13.491 g Al --> 13.5 g Al (3 sig figs)