help with balancing chemical equations?

Question

NH3+O2 yields NO2+H2O

and


Pb(NO3)2 yields PbO+NO2+O2

Answer 1

4 NH3 + 7 O2 ---> 4 NO2 + 6 H2O

2 Pb(NO3)2 ---> 2 PbO + 4 NO2 + O2

The trick is to leave H for next to last and O for last when you are balancing an equation. O2 causes you to double the coefficients in several cases as in these two examples.

Answer 2

Let me give you an easy way to balance equations and some rules and you will be on your way:

Set up a chart like below: This is used to count atoms. It will show you what is balanced and what needs to be balanced. Next, follow the rules to change the numbers (by using coefficients in your equation).

Element Reactant Side Product Side
------------ ------------------- ------------------
N 1 1
H 3 2
O 2 3

Rules:

1. Start with the elements that are NOT H and O if they are out of balance. If they are balanced, then do H, leaving O for last ALWAYS.

In the above example, N is balanced. You see that H and O are 2 and 3 and 3 and 2 respectfully. The least common factor is 6. Place a coefficient in front of the compounds to make 6, changing your numbers in your chart as you proceed. Don't forget to change the N.

Working with H first:

2NH3 + 02 --> NO2 + 3H2O

This now gives you:

N 2 1
H 6 6
O 2 3

Now, go back to N, and place a 2 in front of the product side compound with N.

2NH3 + O2 --> 2NO2 + H2O

This now gives you:

N 2 2
H 6 2
O 2 5

Now, attack the H: Put a coefficient of 3 in front of the product side compound containing the H.

2NH3 + O2 --> 2NO2 + 3H20

This now gives you:

N 2 2
H 6 6
O 2 7

Now, only the oxygen needs balancing. Place a 7/2 in front of the O on the reactant side. Since we cannot have fractional cooeficients, now you need to multiply ALL the cooeficients in the equation by 2 and this will remove the fraction leaving you with the following:

4NH3 + 7O2 --> 4NO2 + 6H2O

For the next equation:

elemnt react prod

Pb 1 1
N 2 1
O 6 5

Start with N by putting a coefficient in front of NO2

This gives you

Pb 1 1
N 2 2
O 6 7

Now, since 6 and 7 are weird, try putting a 2 in front of the Pb(NO3)2 on the reactant side and retry.

This gives you

Pb 2 1
N 4 2
O 12 7

Now, put a 2 in front of PbO on the product side:

This gives you

Pb 2 2
N 4 2
O 12 7

Now, change the coefficient in front of NO2 on the reactant side from 2 to 4. This now gives you:

Pb 2 2
N 4 4
O 12 12

Your balanced equation is:

2Pb(NO3)2 --> 2PbO + 4NO2 + O2

Good luck.

Answer 3

NH3 + O2 --> NO2 + H2O (redox rexn)

The trick is to balance the Hydrogen first, then the oxygen follow by what is remaining.

1) NH3 + O2 --> NO2 + 3/2H2O
2) NH3 + 7/4O2 --> NO2 + 3/2H2O
3) 4NH3 + 7O2 --> 4NO2 + 6H2O (Ans)


Pb(NO3)2 --> PbO + NO2 +O2 (dissociation rxn)

1) Pb(NO3)2 --> PbO + 2NO2 + O2
2) Pb(NO3)2 --> PbO + 2 NO2 + 1/2O2
3) 2Pb(NO3)2 --> 2PbO + 4NO2 + O2 (Ans)

Answer 4

2NH3 + 3.5O2 yields 2NO2 + 3H20

2Pb(NO3)2 yields 2PbO + 4NO2 + O2

Answer 5

4NH3+7O2 yields 4NO2+6H2O

And
2Pb(NO3)2 yields 2PbO+4NO2+O2

Be sure to check my work for errors<;>]

Answer 6

the above answers are correct.