balance these equations

[aman]

1. K2Cr2O7 + H2SO4 + S -----> K2SO4 + (Cr2SO4)3 + SO2

2. P4 + O2 -----> P2O3

3. Na2CO3 + H2O + CO2 -----> NaHCO3

4. CaI2 + HNO3 -----> (CaNO3)2 + NI

[Sonic]

1. K2Cr2O7 + H2SO4 + S -----> K2SO4 + (Cr2SO4)3 + SO2

2. P4 + O2 -----> P2O3

3. Na2CO3 + H2O + CO2 -----> NaHCO3

4. CaI2 + HNO3 -----> (CaNO3)2 + NI

With Balancing the trick is to match up each element one by one on the left and on the right mainly trial and error but you do get a knack for it :)

1. Are you sure that's written out correctly? There is hydrogen on the left but not on the right.

2. P4 + O2 --> P2O3

Check P
left:4. right 2

Therefore we need a 2 on the right to balance:

P4 + O2 ---> 2P2O3

Check O
left:2, right:6

So we need a 3 on O2 on the left:

P4 + 3O2 ---> 2P2O3

This balances in both elements so the final answer is P4 + 3O2 --> 2P2O3


3.Na2CO3 + H2O + CO2 --> NaHCO3

Sodium (Na)
left 2, right 1

Therefore a 2 goes on the right:

Na2CO3 + H2O + CO2 --> 2NaHCO3

Check C
left 2, right 2

Check H
left 2, right 2

Check O
left 6, right 6

Ergo putting a two on the right balances this equation:
Na2CO3 + H2O + CO2 --> 2NaHCO3


4. Hydrogen has disappeared again and are you sure about (CaNO3)2? The NO3 group has a -1 charge and Ca has a +2 charge so Ca(NO3)2 would make more sense. I'd also assume HI is the product instead of NI.

CaI2 + HNO3 -----> Ca(NO3)2 + HI

For that equation I get CaI2 + 2HNO3 ----> Ca(NO3)2 + 2HI using the method above.

[TheMasterMind]

1. K2Cr2O7 + H2SO4 + S -----> K2SO4 + (Cr2SO4)3 + SO2

2. P4 + O2 -----> P2O3

3. Na2CO3 + H2O + CO2 -----> NaHCO3

4. CaI2 + HNO3 -----> (CaNO3)2 + NI
1. incorrect equation (no hydrogen on RHS)

2. P4+3O2-->2P2O3

3. Na2CO3+H2O+CO2-->2NaHCO3

4. incorrect again (missing hydrogen)