# Balancing chemical equations.. HELP?

1. Magnesium metal (Mg(s)) burns brightly in oxygen gas (o2(g)) to produce a whitish-grey powder, magnesium oxide (MgO(s)). Write a balanced chemical equation for this reaction.

2. Magnesium metal (Mg(s)) will also react with copper ion in solution (Cu+2(aq)) to form magnesium ions in solution (Mg+2(aq)) and copper metal (Cu(s)). Write a balanced chemical equation for this reaction.

3. A solution of sodium carbonate (Na2CO3(aq)) will react with a solution of calcium chloride (CaCl2(aq)) to produce the solid precipitate, calcium carbonate (CaCO3(s)) and a solution of sodium chloride (NaCl(aq)). Write a balanced chemical equation for this reaction.

Relevance

from the problem, pick out the reagents and products

Mg(s) + O2(g) ----> MgO(s)

balance the atoms, there are 2 O atoms on the Left hand side of the arrow and only 1 on the right hand side. Put a 2 in front of the MgO

Mg(s) + O2(g) ----> 2MgO(s)

this has unbalanced the Mg, so place a 2 in from of the Mg on the LHS to equalise it

2 Mg(s) + O2(g) ----> 2 MgO(s)

Now it is balanced.

remember that you can only balance equations by placing numbers in front of compounds

2.

Mg(s) + Cu^2+(aq) ---> Mg^2+(aq) + Cu(s)

3.

Na2CO3(aq) + CaCl2(aq) ---> CaCO3(s) + 2NaCl(aq)

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