# What am I doing wrong?

1. Oct 4, 2004

### termite

Here's what I have:
Mass of CuO (copper (II) oxide) = 2.0g
Mass of Cu(metal) = 1.7065g

What I need to find is the mass of oxygen by using the two given above. Do I just do 2.0g-1.7065g=.2935 to get the mass of oxygen or do I do something else?

Last edited: Oct 4, 2004
2. Oct 4, 2004

### Motifs

I am bad at chemistry but is that the complete problem ? :bigsmile:

3. Oct 4, 2004

### termite

It is an experiment. Basically from the two numbers given I have to get the mass of oxygen.

4. Oct 4, 2004

### chroot

Staff Emeritus
Cuprous oxide (copper (I) oxide) is Cu20.
Cupric oxide (copper (II) oxide) is CuO.

You seem to have the two confused. You should start by figuring out which compound you're actually working with.

- Warren

5. Oct 4, 2004

### termite

Sorry for writing CuO incorrectly. Fixed in the initial post.

6. Oct 4, 2004

### Motifs

Your experiment won't get good results, or perhaps it will be zero after all, because you-I mean Y.O.U-don't exactly know much about this either..
What professor has taught you the way to get out the oxygen's mass by such a MINUSING ? That professor I think should go and teach gym than instruct his students such a terrible experiment.
I have seen by my eyes an explosion during an experiment of hidrogen and a student in that traggic accident was terribly injured in her two eyes and got blind then on only because of her stupid ****head professor's carelessness.

Sorry, I think you should CHECK out your papers one more time before making up your mind for this and any further testing/experiment.

Me-Motifs

7. Oct 4, 2004

### chroot

Staff Emeritus
If you started with 2.0g of CuO and performed a reaction to reduce it to plain Cu, the mass of oxygen is indeed just the difference in the two masses.

If you are submitting this to an online homework system, make sure you consider the significant figures in your answer.

- Warren

8. Oct 4, 2004

### chroot

Staff Emeritus
Motifs,

I will respectfully ask that you not post here unless you are capable of staying on topic.

- Warren

9. Oct 4, 2004

### Motifs

I know you must be working really hard for your site,
I admittedly also get angry sometimes for "problems" that are brought about unexpectedly like that....
I am sorry, Okay ? :smallsmile:
Regards,too

Last edited: Oct 4, 2004
10. Oct 4, 2004

### Gokul43201

Staff Emeritus
This question is definitely incomplete. If this is a question from a book or homework, post it exactly as stated.

There is no indication here what the relationship between the copper and the CuO is.

Is the copper got from the reduction of the oxide, or is the oxide made from the copper, or is there something else happening here ?

11. Oct 5, 2004

### chem_tr

Hello,

The reaction should be like that: $Cu~+~ \frac {1}{2} O_2 \xrightarrow {heat} CuO$

So you should first calculate how many moles are there in 2.0 grams of cupric oxide, and learn the mass of oxygen gas from there by using mole-mass equation.

The other mass data about copper may be used to check the calculations, or be used in detecting any impurities of either oxygen gas or copper.

Last edited: Oct 5, 2004