## Problem E.9 in textbook

Gisselle Sainz 2F
Posts: 76
Joined: Wed Feb 21, 2018 3:00 am

### Problem E.9 in textbook

Epsom salts consist of magnesium sulfate heptahydrate.
a) how many atoms of oxygen are in 5.15 g of Epsom salts?

How do we solve this?

AshleyLamba1H
Posts: 30
Joined: Fri Apr 06, 2018 11:03 am

### Re: Problem E.9 in textbook

Firstly, you must find the formula for magnesium sulfate heptahydrate. The formula is MgSO4 · 7 H2O. To find the mass of this molecule, you must add up the molar masses of the individual atoms in the molecule, which gets you 246.48 g/mol. Knowing this will help you find the number of atoms that are in 5.15 g of Epsom salts.

Susu Le 1F
Posts: 30
Joined: Thu Feb 01, 2018 3:01 am
Been upvoted: 1 time

### Re: Problem E.9 in textbook

Using the molar mass of magnesium sulfate heptahydrate (246.48 g/mol) above, you can find the number of moles in 5.15 g of Epsom salts. Once you have the number of moles of Epsom, you can find the number of moles of Oxygen. Finally, you can calculate the number of atoms of oxygen using Avogadro's number.

Carissa Young 1K
Posts: 65
Joined: Fri Sep 28, 2018 12:17 am

### Re: Problem E.9 in textbook

use molar mass to find out the moles of the Epsom salts
5.15 g H14MgO11S / 246.466 g*mol^-1 = .02089 mol H14MgO11S

use the ratio of 11 mols oxygen to 1 mol of Epsom salts and then multiply by Avogadro's number to find how many atoms of oxygen
.02089 mol H14MgO11S * (11 mol O / 1 mol H14MgO11S) *(6.022 * 10^23)
= 1.38 * 10^23 atoms of O