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Percentage composition of copper sulfate hydrate

Q. I have a question... IF anyone can, Please, HELP ME... The percentage composition of copper sulfate hydrate?

Donna Eldenson
- New Brunswick, Canada


Hi Donna. I think you may have left some words out, so I can't quite understand your question. Can you write it out fully, such that it will make complete sense please? I would hate to guess, not only because I could get it wrong, but because it is important that you fully understand the question before you answer your assignment -- and it's not super clear that you do :-)

Ted Mooney
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


A. All I know is that there is 36% H2O.

Elspeth Weldon
- Raleigh, North Carolina


thumbsup2Copper sulphate pentahydrate is CuSO4.5H2O. If you look up the atomic weights of Cu, S, O, and H, and multiply how many atoms of each are in the compound per the formula above, you'll see that Elspeth is right on.

Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

February 7, 2009

Q. How can I figure out the concentration (in mg/L) of Cu from copper sulphate when the concentration of CuSO4 is 3g/L?

Derek Robinson
- Toronto, Ontario, CANADA

February 18, 2009

A. Hi, Derek. This sounds like an easy homework question carefully designed to warn you that you didn't understand the lesson. What does the formula CuSO4 mean to you? It should mean a molecule that contains an atom of Cu, an atom of Sulfur, and four atoms of oxygen. Did you look up the atomic weights of these elements as the first step like we suggested? You simply divide the atomic weight of copper by the atomic weight of the whole copper sulphate molecule to learn the percentage by weight of copper in copper sulphate. Good luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

February 13, 2011

Q. Hello, can anyone please help me with these answers. Thank You

1. what is the percentage copper in copper sulfate (Cuso4)?
2. What mass of copper can be obtained from 2.34 g of Cuso4?
3. The calculated mass of copper is different from (less than) the actual mass of copper carbonate. This is likely to be because:

Andrew Q [last name deleted for privacy by Editor]
student - Bogota, Colombia

February 14, 2011

A. Hi, cousin . This is not a site where people do your homework for you; rather, it's a place where people will try to help you understand.

So first off, when doing chemistry you must take the time to capitalize correctly or you will be hopelessly confused. Every element is represented by either a single upper case letter, or by two letters where the first is upper case and the second is lower case. "Cu", for example, means copper, but "CU" means carbon plus uranium, and "cu" is meaningless. Although someone might be able to guess that you meant "copper sulfate" when you wrote "Cuso4", you will find yourself unable to progress until you employ the discipline of capitalizing the symbols properly.

Your first question was answered immediately above your question. If you didn't understand, please write your question in terms of what you don't understand rather than pasting it from your homework assignment. Once you have the answer to your first question, the answer to the second is obvious. Sorry, I don't quite understand the third question. Good luck!


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

April 22, 2012

Q. I want to determine the chemical formula for a hydrate.
The hydrate is Copper(II) Sulfate or CuSO4
After conducting the experiment I found the mass percentage of this compound is:
28.4% water
71.6% copper(II) sulfate

This is how I find the number of hydrates in the solution:
CuSO4.xH2O (where x is the number of hydrates)

Assume 100 g sample

28.4 g of water, 71.6 g of copper(II) sulfate

Number of moles of water in this sample = 28.4 g/ molar mass of water( 18.02 g/mol)

= 1.576 mol

Number of moles of copper sulfate in this sample = 71.6 g / (159.62 g/mol)

= 0.449

Divide by the smallest mole number to get a whole number ratio

0.449/0.449 = 1
1.576 /0.449 = 3.51


From here do I round up to 4 so the ratio is 1 copper sulfate molecule for every 4. Or do I multiply by 2 so I have a 2:7 ratio?

Cyrus D.
- Toronto, Ontario, Canada

April 26, 2012

A. You have two possibilities:
1. Your analyses method was not the best.
Sometimes the last water is a bit hard to drive off. Crushing the crystals will give you a lot more surface area. Weigh the powder, not the crystals.
Did you check the weigh boat after the "wet" weight to see if any remained?
You could repeat the process and see if any more water will come off. Too aggressive a drying might have driven off a tiny bit of the copper compound with the moisture (steam). Sometimes the crystals will pop like popcorn.
Is your balance accurate enough? Was it calibrated before you started?
Did you leave enough time for the temperature to equilibrate after the drying?

2. You might be working with a mixture of water of hydration.

A normal lab experiment is run in triplicate. How do your 3 runs agree?

What does your teacher think??

James Watts
- Navarre, Florida

April 29, 2012

thumbsup2My teacher told me to round to 4. And yes you are right the correct ratio is 1:5. I didn't fully heat the compound so I guess that's just going to be my source of error!


Cyrus D.
- Toronto, Ontario, Canada

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