Help with Chemistry work on mass? Watch

clucky_chick
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Hello,

I have been having problems figuring out these two questions for my Science teacher, he is very strict, and I would be grateful for some guidance on to how to solve these two questions. I have to show the answer, and working out, to show a method I could use in my exam next year, soon

1) How much carbon dioxide can be produced from 10kg of Sodium Carbonate?
2) How much aluminium oxide is needed to produce 500 tonnes of aluminium?

It would be great if you could help me answer these questions, as I am not the brightest bulb in the box.

Thank you!
-Clucky_Chick
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Borek
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Start with reaction equations.
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clucky_chick
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(Original post by Borek)
Start with reaction equations.
Reaction equations????

We have not been taught that?
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Borek
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Then I don't see how you can be asked about stoichiometry.

That is, it is possible to solve these problems without reaction equations, but it requires understanding that you typically learn through solving stoichiometry problems based on reaction equations.

Do you know what is aluminum oxide formula? Can you calculate what is mass percentage of aluminum in the aluminum oxide?
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clucky_chick
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(Original post by Borek)
Then I don't see how you can be asked about stoichiometry.

That is, it is possible to solve these problems without reaction equations, but it requires understanding that you typically learn through solving stoichiometry problems based on reaction equations.

Do you know what is aluminum oxide formula? Can you calculate what is mass percentage of aluminum in the aluminum oxide?
I have a slight idea how to calculate it, but I do not really understand. Sorry to be a pain!
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clucky_chick
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Basically we were told to find a method and work out one of these in class, and I found a method, but it is confusing. Plus, that is in class, which is annoying, as I do not remember the whole method. We have been told to research, as our teacher does not want to 'dictate' in front of the whole class, and needs us to learn it ourselves.
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Borek
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Start with the formula. Calculate molar mass of the oxide. Calculate molar mass of just the aluminum present. What is the fraction of the metal in the oxide? You want 500 tonnes of the metal - set up a ratio and solve for the oxide mass.
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clucky_chick
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I am rubbish with Maths too!

The formula for Aluminum Oxide is AL203
The Molar Mass is
101.96 g

I do not really know how to calculate a fraction of the metal in the oxide, and I can not do ratios!

I'm only in Yr10, and we are not usually asked anything that we have no idea about!
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Borek
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Molar mass is OK.

Now, there are two atoms of Al in the molecule. What is their mass?
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clucky_chick
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(Original post by Borek)
Molar mass is OK.

Now, there are two atoms of Al in the molecule. What is their mass?
The mass for one is 27? So wouldn't two be 54?
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Borek
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Yes.

Now, regardless of the mass of the oxide, ratio of metal mass to the oxide mass is always the same:

\frac {metal\ mass}{oxide\ mass} = \frac {55\ g} {102\ g} = \frac {500\ tonnes}{x\ tonnes}

Solve for x.
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clucky_chick
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So the ratio of the oxide would be 500 tonnes too?
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Borek
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(Original post by clucky_chick)
So the ratio of the oxide would be 500 tonnes too?
Ratio is not a single number. Ratio is something to something (or something over something).

Let's say you can buy 3 Underground tickets for 5 pounds (you probably can't now, but I wasn't to London for over a decade). Ticket to pound ratio is 3:5

\frac {3\ tickets}{5\ pounds}

This ratio doesn't depend on the number of tickets, nor number of pounds, it is always constant. So, if you have 20 pounds, you know the ratio is still 3:5

\frac {3\ tickets}{5\ pounds} = \frac {n\ tickets}{20\ pounds}

and you can easily solve for number of tickets that can be bought for 20 pounds:

{n\ tickets} = \frac {3\ tickets \times 20\ pounds}{5\ pounds} = 12\ tickets

That's just a simple algebra at work.

(I am not convinced it is the best example, but we have to start with something, don't we?)
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clucky_chick
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Okay, I understand that. But I am unsure of how you could really work out the Ratio/Equation thing. I understand the once you just explained???
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Borek
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I wrote the ratio for the aluminum and aluminum oxide problem earlier - just compare with the above.
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clucky_chick
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Thank you, I was able to get help at school too. I think I understand now, and I am very grateful of your help!
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