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# Im doing a past paper and im confused on a few of the answers?

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1. 1.12g of iron reacts with oxygen to form 1.60g of an oxide of iron. what is the formula of this oxide of iron? I know the answer is Fe2O3.
1.12/ 56 = 0.02
1.60 / 16 = 10

how does this become a ratio?

2) in an experiment 1.226g of Kclo3 was heated. A mass of 0.32g of oxygen gas was collected. What is the oxygen percentage yield fort he experiment??

0.320g / (0.320/16) = 0.02 --> 0.320/0.02 = 6.4 *100

I know its wrong but im confused :/
2. (Original post by Hazel99)
1.12g of iron reacts with oxygen to form 1.60g of an oxide of iron. what is the formula of this oxide of iron? I know the answer is Fe2O3.
1.12/ 56 = 0.02
1.60 / 16 = 10
how does this become a ratio?
You need to use the mass of oxygen that has reacted
1.60g is not the mass of oxygen
mass of oxygen=1.60-1.12=0.48g
0.48/16 = 0.03
1.12/56 = 0.02
Therefore Fe : O is 2 : 3

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