[jess870]

2ZnO + C --> 2Zn + CO2
2(Au+3) + 3Zn --> 3(Zn+2) + 2Au

There's two reactions that take place here which makes this confusing.
My Question:
If excess carbon was added, how many grams of gold metal should be produced if 1.59 g of ZnO were completely used up?

[Corribus]

You need to show your work to receive help. This is a forum policy.

If you don't like the fact that it is two reactions, add them together to form one. This will require rebalancing and cancellation of like terms.

[jess870]

2ZnO + C --> 2Zn + CO2
2(Au+3) + 3Zn --> 3(Zn+2) + 2Au

There's two reactions that take place here which makes this confusing.
My Question:
If excess carbon was added, how many grams of gold metal should be produced if 1.59 g of ZnO were completely used up?

Okay, so you would start with the given and use (1 mole ZnO)/(81.39 g ZnO) to cancel out that given. What I'm confused about is the molar ratio. Would the molar ratio of Zinc Oxide to Gold be 2 to 2 or would there be a step in between?

[Corribus]

For the moment, just stick to moles. Just by inspection of the stoichiometry, you can determine the relationship between the products and reactants.

By the first equation, 2 moles of ZnO will produce 2 moles of Zn.
By the second equation, 3 moles of Zn will product 2 moles of Au.

Therefore, 1 mole of ZnO will produce how many moles of Au? The answer is

1 mole ZnO X (2 moles of Zn / 2 moles of ZnO) X (2 moles of Au / 3 moles of Zn), or 2/3.

As I was trying to tell you in your other thread, if having two equations confuses you, you can combine them into one so that it is more straightforward to see the molar relationship. This does require that you balance your new equation.

I.e., you can add the left hand side of each equation and the right hand side of each equation thusly:

2ZnO + C + 2Au³⁺ + 3Zn  2Zn + CO₂ + 3Zn²⁺ + 2Au

You'll notice that the amount of Zn on the left hand side does not equal the amount of Zn on the right hand side, so this new equation isn't balanced. You can balance it easy enough by multiplying everything on the left by 2 and everything on the right by 3 to get:

4Zn + 2C + 4Au³⁺ + 6Zn  6Zn + 3CO₂ + 9Zn²⁺ + 6Au

Now it should be clear that 4 moles of Zn yields 6 moles of Au, or 1 mole of Zn yields 2/3 moles of Au. Effectively you've done the same thing via both procedures, but sometimes it is easier to see it when it's in one reaction equation.

Once you have the mole ratios figured out, you can do your mass conversion and solve the problem.

[jess870]

@Corribus
Thanks so much. That's what I thought I should do, but some of my classmates were going straight from ZnO to Au so I got confused.
Also, thanks @billnotgatez for combining it. This is the first forum I've been to so I wasn't sure how to work everything. And yes, I should have read the directions and rules, but I'm a lazy teenager so I mistakenly didn't.

[Corribus]

In retrospect, please ignore the combining equations part of my earlier post. I was doing that while I was trying to have a conversation on the phone (never a good idea) and looks like I completely botched it. Those equations still aren't balanced, lol. You can still do this method, but you have to do the multiplying before you add the equations to get the right answer. I hope I didn't confuse you further.