## E.9 Chemical Principle 7th edition

Ziyan Wang 3J
Posts: 51
Joined: Wed Sep 18, 2019 12:22 am

### E.9 Chemical Principle 7th edition

Epsom salts consists of magnesium sulfate heptahydrate. Write its formula. (a) How many atoms of oxygen are in 5.15 g of Epsom salts? (b) How many formula units of the compound are present in 5.15g? (c) How many moles of water molecules are in 5.15g of Epson salts?

zfinn
Posts: 106
Joined: Fri Aug 30, 2019 12:16 am

### Re: E.9 Chemical Principle 7th edition

this is how I solved it - let me know if you have any questions!

405268063
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am

### Re: E.9 Chemical Principle 7th edition

E9)
Magnesium sulfate = MgSO4; Heptahydrate = 7 H2O
Use Avogadro's number to convert between atoms and mols
a. (5.15 g / 246.48 g/mol)(11 O atoms / 1 mol MgSO4 7H2O)(6.022 x 10^23 atoms / 1 mol) = 1.38 x 10^23 O atoms
b. (5.15 g / 246.48 g/mol)(6.022 x 10^23 atoms / 1 mol) = 1.26 x 10^23 atoms
c. (5.15 g / 246.48 g/mol)(7 mol H2O / 1 mol MgSO4 7H2O) = 0.146 mol

Anthony Hatashita 4H
Posts: 103
Joined: Wed Sep 18, 2019 12:21 am

### Re: E.9 Chemical Principle 7th edition

For part a I found out how many grams of O were in the total 5.15 grams, and from there I converted that amount to moles and found the amount of O atoms that way. I got the same answer as the other responses, but this helped me visualize it better.