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Balanced Symbol Equations

Asked by xhayleyx | Oct 18, 2002 | GCSE Level > Chemistry > Homework
xhayleyx
xhayleyx asks:

What would be the balanced symbol equations when:

1) Copper oxide reacts with sulphuric acid producing copper sulphate and water? Also, how many moles and grams of copper sulphate would be made from 0.5 moles of copper oxide?

2) Magnesium oxide reacts with hydrochloric acid forming magnesium chloride and water? Also, how many moles and grams of products would be made from 0.2 grams of magnesium oxide?

3) Calcium hydroxide reacts with nitric acid forming calcium nitrate and water? Also, how many moles of acid are necessary to react with 4 moles of calcium hydroxide? How many moles and grams of product are made?

etutor answers:
1) Copper oxide reacts with sulphuric acid producing copper sulphate and water? Also, how many moles and grams of copper sulphate would be made from 0.5 moles of copper oxide?

Equation is:
CuO + H2SO4 --> CuSO4 + H2O

(Note - the numbers in the formulae should be subscript.)

This equation tells us that 1 mole of copper oxide reacts with 1 mole of sulphuric acid to produce 1 mole of copper sulphate and 1 mole of water. So if you started with 0.5 moles of copper oxide you would end up with 0.5 moles of copper sulphate.

To work out how many grams this is, you need to calculate the relative molecular mass (your teacher may have called this the formula mass). You need to know the relative atomic masses (you can get this from the Periodic Table)
CuSO4 contains 1 atom of Cu of mass 64, 1 atom of sulphur of mass 32 and 4 atoms of oxygen, each of mass 16 giving 64 (4 x 16). Add this up and it comes to 160. This means that 1 mole of copper sulphate weighs 160g. So 0.5 moles will weigh 160 x 0.5 = 80g.


2) Magnesium oxide reacts with hydrochloric acid forming magnesium chloride and water? Also, how many moles and grams of products would be made from 0.2 grams of magnesium oxide?

The equation would be:
MgO + 2HCl --> MgCl2 + H2O
This tells you that 1 mole of MgO reacts with 2 moles of acid to give one mole of each of the products.

1 mole magnesium chloride will weigh 24 + (2x35.5) = 95g. Therefore 0.2 moles will weigh 95 x 0.2 = 19g
1 mole of water weighs (2x1) + 16 = 18g. Therefore 0.2 moles will weigh 18 x 0.2 = 3.6g.

3) Calcium hydroxide reacts with nitric acid forming calcium nitrate and water? Also, how many moles of acid are necessary to react with 4 moles of calcium hydroxide? How many moles and grams of product are made? Ca(OH)2 + 2HNO3 --> Ca(NO3)2 + 2H2O

Eqaution tells you that 1 mole of hydroxide reacts with 2 moles of acid. So if you had 4 moles of hydroxide it would need 8 moles of acid.

4 moles of hydroxide will give 4 moles of then product. Mass of product is 40 + (2x14) + (6x16) = 164g. This is one mole, so 4 moles will be 4 x 164 = 656g.

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