Can anyone explain to me how to balance a chemical equation? im having trouble in understanding how i keep getting it wrong.

To balance a chemical equation, one has to make the total number of molecules of each element equal on both sides of the equation.

For example,

in the reaction of sodium (Na) and chlorine (Cl2), we get sodium choride (NaCl)

Na + Cl2--->NaCl

Now one chlorine molecule contains 2 atoms of Cl and one Na molecule contains 1 atom of Na

To balance, we have to take 2 Na molecules,

2Na + Cl2 - - - > NaCl

Balancing both sides we get

2Na + Cl2 = 2NaCl

Here both sides of the chemical equation contains equal number of molecules of each element, so it is a balanced equation.

For example we are going to use this unbalanced chemical reaction:

H₂ + O₂ → H₂O.

First, calculate number of atoms (hydrogens and oxygens) on left and right. There is two oxygen and two hydrogen on left and two hydrogen and one oxygen on right.

You can not change molecular formula of compound, only you can put coefficient in fron of compound to balance reaction.

Put 2 in front water to balance oxygen (now you have two oxygens on left and right). But now you have four hydrogens on right, so you must put 2 in fron hydrogen on the left.

2H₂ + O₂ → 2H₂O.