How do get the mass and moles?

Question

I just need someone to kind walk me throught this one: How much mass does

1 mole of Fe2(SO4)3 have?

How many moles are in

180 grams of C6H12O6

Answer 1

1. To find the mass, first you need to find the atomic mass of each atom in the molecule. So:
Fe = 55.84 * 2 = 111.68
S = 32.07
O = 16 * 4 = 64
and the (SO4) unit has 32.07 + 64 = 96.07
Since there are three SO4 units in the molecule, thats 96.07 * 3 = 288.21 ; and adding the Fe, that's a total of 399.89 atomic mass units in the whole molecule.

That means that one mole of this molecule weighs 399.89 grams.

2. Similar procedure: first add up the atomic masses of each atom in the molecule.
C = 12.01 * 6 = 72.06
H = 1.008 * 12 = 12.096
O = 16 * 6 = 96
for a total of 180.156 atomic mass units in the whole molecule. That means that 180.156 grams would be exacly one mole, and we want to know how many moles in exactly 180 grams. So the answer is just a bit less than one mole, or 180 / 180.156, or .999134 moles.

Answer 2

If you want to go from moles to grams, you look up the masses of each of the elements of Fe2(SO4)3. There are 2 Fe atoms, so you multiply the atomic mass by 2. There are also 3 S atoms here, and 7 O atoms. You add those masses and multiply by the number of moles asked.

To convert grams to moles, you again look up the atomic masses of C6H12O6. There are 6 C atoms, so you multiply the atomic mass of it by 6. You add all those masses together and divide it by 180grams to get the moles.

I didn't want to do it out for you, because I know that you can do it. So, go ahead and take the periodic table, a calculator and try it yourself! I hope the explanations helped. Oh, seems like other people already did it for you.

Answer 3

No. of moles = mass in g/ Mr. [Fe2(SO4)3]
so mass = 56*2 + (32+64)*3
= 400g

Try to do the other one yourself as a practice. Same formula apply. ans shld be 1.

Hope it helps=)
and good luck