Question

If hydrogen is combined with oxygen in the ratio 1 is to 8 to form H2O. Calculate number of moles of O required to form H2O?

Answer 1

Answers

First we have to find the mass of the following, 
10 mole of hydrogen will weigh 10 x 2 g = 20 g
And 5 moles of oxygen wil weigh 5 x 16 g = 80 g

Now we know hydrogen and oxygen in 1:8 ratio
So we get that if we take 20 g of H2 as 1 x then it needs 160 g of O2
So we take 80 g of O2 as 8x and thus it needs 10 g of H2, which is available
So they would combine to form 
80 + 10 = 90 g of water

Now we know molecular mass of water is 18 g

So its forms 90/18 = 5 moles of water

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