## E23 Confused

Ruth Rosales 3D
Posts: 40
Joined: Wed Sep 30, 2020 9:44 pm

### E23 Confused

Calculate the amount (in moles) of (a) Cu^2+ ions in 3.00 g of CuBr2

The first time I solved this question, I moved on because my response matched. However, now that I am reviewing the questions I am rethinking why is the answer 0.0134 mol of Cu^-2 and not 0.0134/2 mol of Cu^-2.?

3.00 CuBr2/223.35 g CuBr2mol^-1 = 0.0134 mol CuBr2 and since the molar ratio is 1 Cu:2 Br shouldn't we divide the value by 2?
Last edited by Ruth Rosales 3D on Wed Oct 14, 2020 9:00 pm, edited 1 time in total.

Charlene D 3I
Posts: 45
Joined: Wed Sep 30, 2020 9:54 pm

### Re: E23 Confused

Hi Ruth!
The you are given the grams of CuBr2, which you can then convert to mols of CuBr2 using the molar mass. Because molar mass corresponds to the amount of grams in one mole of CuBr2, you can simply multiply the mols of CuBr2 by the molar ratio of 1 mol Cu : 1 mol CuBr2 to find mols of Cu^2+ ions.
I hope this helped. Let me know if you have any other questions.

aashmi_agrawal_3j
Posts: 54
Joined: Wed Sep 30, 2020 9:39 pm

### Re: E23 Confused

The ratio is actually 1:1 between moles of Cu ions and CuBR2 so you don’t have to divide the value by 2.

SophiaBarden 3H
Posts: 46
Joined: Wed Sep 30, 2020 10:07 pm

### Re: E23 Confused

We only look at the ratios between the same element when looking at the ratio of Cu and CuBr2. So there is 1 Cu : 1 Cu

Thomas Gimeno
Posts: 40
Joined: Wed Sep 30, 2020 9:49 pm

### Re: E23 Confused

Because there is one atom of Cu in CuBr2, for every mole of CuBr2 you have one mole of Cu. I think you might be looking at the Br2 and thinkcing that's why you divide by however the fact that there are 2 Br atoms does not change the ratio between Cu and CuBr2.