balancing equations?

Question

how do you do these?

14) NH3 + H3PO4 ----> (NH4)3PO4
15)NH3 + O2 ----> N2 + H2O
16) Fe2O3 + H2 ----> Fe +H2O
17) PbO2 + CO ----> Pb + CO2
18) Al + Fe2O3 ----> Fe + Al2O3
19) Fe3O4 + C ----> Fe + CO2
20) H20 + Co ----> H2 + CO2

and the numbers are meant to be small but i can't do them like that? so does any one know how to do these? I really really need help, very apreciated :D

Answer 1

14)3NH3 + H3PO4---------> (NH4)3PO4
15) 4NH3+3o2---------> 2N2+6H2O
16) Fe2O3+3H2-----> 2Fe+3H2O
17) PbO2 + 2CO---->Pb+2CO2
18)2Al+Fe2O3---->2Fe+Al2O3
19)Fe3O4+C------>3Fe+2CO2
20)H2O+CO------->H2+CO2

Answer 2

To balance these you will put fairly small numbers in front of some of the substances in each reaction. It is largely a matter of logic and trial-and-error to get them to balance.

14. Since the right side has 3 N atoms in it, start by putting a 3 in front of NH3 on the left. That should balance that one.

15. Since you have 2 N atoms on the right, try putting a 2 in front of NH3 on the left. That balances N, but now you have 6 H atoms on the left, so try putting a 3 in front of H2O on the right to give you 6 Hs on the right. Now, you have 3 O atoms on the right and can put a 1.5 or a 3/2 in front of O2 on the left. It is not too good to have fractional coeffients, so multiply all of your coefficients by 2 to get rid of the fraction. That will leave you with:
4 NH3 + 3 O2 --> 4 N2 + 6 H2O

You'll just have to play with the rest of them. Some are pretty easy, and others will take a little work.

Good luck.