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# Concentration of product question? watch

1. Hi all,

I am doing a SKE in chemistry and stuck with something...

The question is: Zinc reacts with phosphoric acid to form zinc phosphate and hydrogen gas.

Reaction uses 13.08 g of zinc in 0.500 dm3 of phosphoric acid solution...

So what I have done is

relative mass of zinc is 65.4
13.08 g of zinc

65.4/13.08 = 0.2 moles of zinc

0.2 / 0.500 dm3 = 0.4 mol dm-3

How do you work out volume of hydrogen given off?

Equation is: 3Zn + 2H3PO4 = ZN3(PO4)2 + 3H2

Thanks
2. (Original post by Lambert87)
Hi all,

I am doing a SKE in chemistry and stuck with something...

The question is: Zinc reacts with phosphoric acid to form zinc phosphate and hydrogen gas.

Reaction uses 13.08 g of zinc in 0.500 dm3 of phosphoric acid solution...

So what I have done is

relative mass of zinc is 65.4
13.08 g of zinc

65.4/13.08 = 0.2 moles of zinc

0.2 / 0.500 dm3 = 0.4 mol dm-3

How do you work out volume of hydrogen given off?

Equation is: 3Zn + 2H3PO4 = ZN3(PO4)2 + 3H2

Thanks
At room temperature 1 mole of gas occupies about 24 litres
3. you know 1 mole of any gas at standard temperature and pressure has a volume 24 litres. So what volume does 0.2 moles of hydrogen have?
4. Thanks both.

So is it 0.4 if Hydrogen is diatomic?

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5. One mole of Zn produces one mole of H2.

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