Question #729cf

2 Answers
Nov 29, 2017

576g

Explanation:

Al2(SO4)3 has 3 x 4 = 12 oxygen atoms

that weigh 16g/m apiece. Therefore

3mole x 16g/mole x 12 = 576g

= the mass of oxygen contained in 3moles Aluminum Sulfate.

Nov 29, 2017

1.68 grams O.

Explanation:

First, calculate the number of moles of Al_2(SO_4)_3 in 3.0 moles. Then multiply by 12 to get the total number of O moles (or we can us 6 for O_2 - just don't get them confused). Finally, multiply this by the molecular weight of O to get the final value in grams.

Al_2(SO_4)_3 = 342 g/"mol"

3.0/342 = 0.00877 moles Al_2(SO_4)_3

0.00877 xx 12 = 0.105 moles O
0.105 xx 16 = 1.68 grams O

CHECK:
Mass% O in Al_2(SO_4)_3: 192/342 = 56.14%
0.5614 xx 3.0 = 1.68 Correct.

(OR, do the check and calculation in the reverse order, if you like.)