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# CIE AS level Chemistry watch

1. Which equation correctly describes the complete combustion of an alkene, CnH2n?

A CnH2n + 3/2n O2 → nCO2 + 2n H2O
B CnH2n + 3/2n O2 → nCO2 + nH2O
C CnH2n + 2n O2 → nCO2 + nH2O
D CnH2n + 2n O2 → nCO2 + 2n H2O

Can anyone help me with this question? The answer scheme says it's B.
2. What is hard?

Can you balance equations?
3. (Original post by Pigster)
What is hard?

Can you balance equations?
I have my exam next week and i would just like to know how to solve this question. I'm not simply trying to get you to finish my homework or anything like that. If i knew how to solve this question i wouldn't be posting it here. This is for my own revision. I would really appreciate it if you could explain this question to me.
4. Still my questions are valid.

What are you finding hard about it?

I can only think that you find balancing equations difficult, but it might be something else.

CnH2n is constant on the left, and nCO2 is constant on the right, that only leave the number of H2O and number of O2 to find. It looks to me like a fairly trivial AS question. Certainly something that a good GCSE student should be able to do.
5. (Original post by Pigster)
Still my questions are valid.

What are you finding hard about it?

I can only think that you find balancing equations difficult, but it might be something else.

CnH2n is constant on the left, and nCO2 is constant on the right, that only leave the number of H2O and number of O2 to find. It looks to me like a fairly trivial AS question. Certainly something that a good GCSE student should be able to do.
It's alright i figured it out already. Thank you.

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