Question

What is the mass of 2.56 × 10–4 moles of Fe2O3?

A. 4.09 × 10–2 g

B. 159.6 g

C. 6.23 × 105

D. 1.60 × 0–6 g

Answer 1

first find the molecular weight of Fe2O3

Answer 2

molecular weight of Fe2O3 =56*2 +16*3 =112+48=160

Answer 3

now by definition of mole
1 mole of Fe2O3 weighs 160 g

Answer 4

hence
2.56 × 10–4 moles of Fe2O3 must weigh 2.56 × 10–4 * 160 g....

Answer 5

@Joshyface I think this should be posted in Chemistry. Please post chemistry question in Chemistry subject now onwards.
http://openstudy.com/study#/groups/Chemistry

Answer 6

@@Joshyface
its 2.56*160/10000 g = 4.09 × 10–2 g
so option A