Answer:
To balance a chemical equation, ensure that the number of each atoms are the same on both sides.
Let's look at Q13:
On the left, you have 1 Mg, 1 Cu and 2 Cl.
On the right, you have 1 Mg, 1 Cu and 2 Cl.
This means that the equation is already balanced.
Most of the time, we balance H and O the last.
Q5. is combustion.
This is because you have an alkane reacting with oxygen to produce carbon dioxide and water.
Q9. is also a combustion reaction.
Decomposition is like breaking down a substance.
Q1 and Q10 are decomposition reactions.
Displacement reaction are when they have their 'partners' swapped. Q6 is a displacement reaction.
Q3 is a combination reaction