balancing equations

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Reviser4689
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#1
Report Thread starter 5 years ago
#1
how do you know which elements to put in? I really don't understand how you are supposed to know :/
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Dysf(x)al
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#2
Report 5 years ago
#2
If you aren't given the equation, you'll have to work it out. Either it's one you're expected to learn (e.g. respiration, photosynthesis) or you can figure it out. Use the ions table to find the right formulae for compounds. For example, calcium has a 2+ charge and chloride has a 1- charge, so calcium chloride is CaCl2 (you need it to add up to zero). If you are missing a reactant, think about what's left over. The first things you should try are O2, H2O, CO2 and H2.

When you balance, you want one side to be equal to the other. If there are 3 carbon atoms on one side you'll need 3 on the other. If the only compound with carbon in on the other side is CO2, you need a 3 in front of this. You might have to change this as you add more numbers. At the end, check that nothing has been created or destroyed - that would be against the laws of chemistry!
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Yorrick
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#3
Report 5 years ago
#3
As stated above, you will probably be given the elements and asked to put numbers in front of them. There are some equations on the specification that you will need to know. I have attached a list of the equations, both balanced for quick revision or unbalanced for practise, along with a booklet called ULTIMATE balancing equations which takes you through every equation you need to balance.

However, balancing will probably be 2 marks at most, so don't spend too much time on it and if you don't get it at all, I suggest you just let it go for C1 or at the most, go through the list of balanced equations just in case they come up.
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