[Viral]

When referring to Cu, we are using the Cu-12 isotope.

1. The problem statement, all variables and given/known data

Calculate what mass of carbon you would need to reduce 15.9g of copper(II) oxide to copper by the reaction:

CuO_(s) + C_(s) [tex]\rightarrow[/tex] Cu_(s) + CO_(s)

2. Relevant equations

n = m / ar
(number of moles = mass / relative atomic mass)

If you know any more, it would be really useful for me though .

3. The attempt at a solution

Ar(Cu) = 63.5
Ar(O) = 16.0
Ar(C) = 12.0

CuO = 1 / (63.5 + 16.0) = 79.5g
C = 1 / (12.0) = 12.0g

79.5 / 79.5 * 15.9 = 15.9g of CuO
12.0 / 79.5 * 15.9 = 2.4g of C

Basically, I divided the mass of CuO by the mass of CuO and multiplied by 15.9 to get 15.9g (as in the question). Then, I applied the same equation to C by dividing the mass of C by 79.5 and then multiplying by 15.9 to get 2.4g, which is my answer.

Is this correct?

[Borek]

When referring to Cu, we are using the Cu-12 isotope.

You sure you mean copper?

79.5 / 79.5 * 15.9 = 15.9g of CuO

Hardy suprising result - it is about as good as proving 1=1.

12.0 / 79.5 * 15.9 = 2.4g of C

That's correct - but I am not sure if you know why. It will became obvious once you will start doing questions where stoichiometry is not 1:1.

[Viral]

I was actually referring to C, not Cu >.< .

I just see it as an equation, and whatever I do to one side, must be done to the other. Is there an actual equation that I am supposed to use for this?

[Borek]

But why do you want to calculate mass of CuO, it it is given?

[Viral]

It was just my working out, on how I would get to 15.9g from 79.5. There's no effect on the final answer, it just made it easier for me to understand.