## HW #E9

Posts: 72
Joined: Wed Sep 18, 2019 12:18 am

### HW #E9

For this problem, I'm having trouble understanding how I'm supposed to go from Epsom salt to only the atoms of oxygen. I know I have to be able to get the moles of oxygen, but what steps do I need to take before? Thank you :)

Ami_Pant_4G
Posts: 106
Joined: Sat Aug 24, 2019 12:17 am

### Re: HW #E9

So to get moles of oxygen you will have to first determine the number of moles of Epsom salt, which you would find by multiplying 5.15 by the molar mass. then to get to moles of oxygen from moles of Epsom salt you'll have to multiply by the ratio 1 mole Epson salt to 11 moles oxygen. And then to get the number of atoms you multiply by Avogadro's number. Hope this helps!

Ali Polansky 1A
Posts: 15
Joined: Fri Aug 09, 2019 12:15 am
Been upvoted: 1 time

### Re: HW #E9

You need to use the molar ratio of moles per oxygen atom to moles of Epsom salt. (11 to 1)
(Four of the oxygen moles come from Epsom salt and seven come from the water)

magnesium sulfate heptahydrate= MgSO4 7H2O

Abby Soriano 1J
Posts: 103
Joined: Sat Aug 24, 2019 12:16 am

### Re: HW #E9

You have to convert the mass of the salts into moles using the molar mass of its formula (MgSO4 7H20). From there, you can use a conversion factor of 11 moles of oxygen (there are 11 oxygens counted in the formula) / 1 mole of the salt to find your moles of oxygen. Then you can use Avogadro's number to go from moles of oxygen to the actual number of oxygen atoms.