Balancing Cemical Equations?

Question

Na+H2O-->NaOH+H2
Si2H3+O2-->SiO2+H2O
C7H6O2+O2-->CO2+H2O
FeS2+O2-->Fe2O3+SO2
I4O9-->I2O6+I2+O2

Answer 1

I will do the first one for you.
Na+H2O-->NaOH+H2
There must be equal numbers of elements on each side of the arrow.
Count them.
1 Na -> 1Na
1 O ->1O
2H2 -> 3H2 - We need to increase the amount of hydrogen on the left hand side. The problem here is is that there is an odd number of hydrogens on the right hand side.

Put a two infront of the NaOH to make the right hand side and even number of hydrogens.
Na+H2O-->2NaOH+H2

Then put a 2 infront of the H2O
Na+2H2O-->2NaOH+H2

Ok, now we have 4 hydrogen on either side. But notice that we now have 1 Na on one side of the arrow and 2 on the other. Put a 2 infront of the Na
2Na+2H2O-->2NaOH+H2

Check to see if it is balanced
2Na -> 2Na
2O -> 2O
4H -> 4H
Balanced!!!

Answer 2

Tell ya what, I'll work ONE out for you and explain step by step what I am doing.

Take the second equation: Si2H3 + O2 --> SiO2 + H2O

STEP 1: Choose any one of the elements and balance it by using coefficients in front of molecules. Let's start with the silicon (Si). You have 2 Si on the left and 1 on the right. What number can you multiply 1 by to get 2? the answer is 2. So place a 2 in front of SiO2: Si2H3 + O2 --> 2SiO2 + H2O

STEP 2: Pick another element and balance. You now have 2 O on the left and 5 O on the right. So on the left you need a 5/2 in front of the O2 on the left (yes, you can have fractions as long as you eliminate them at the end):
Si2H3 + 5/2O2 --> 2SiO2 + H2O

STEP 3: Eliminate the fraction by multiplying every single molecule by 2: 2Si2H3 + 5O2 --> 4SiO2 + 2H2O

STEP 4: Balance H by replacing the 2 in front of the H2O with a 3. This equals out the hydrogen:
2Si2H3 + 5O2 --> 4SiO2 + 3H2O

STEP 5: Now your O are unbalanced (yes it really can go back and forth like this). You have 11 O on the right and 10 on the left. You need 1 O but every number you increase O2 by increases the number of O by 2. To solve this, simply add 1/2 to the coefficient: 2Si2H3 + 11/2O2 --> 4SiO2 +3H2O

STEP 6: Now your equation is balanced but again you have to eliminate fractions. Multiply through by 2:
4Si2H3 + 11O2 --> 8SiO2 + 6H2O

Balancing is merely a LOT of trial and error. Use a pencil.

Answer 3

2Na+2H2O-->2NaOH+H2
2Si2H3+11/2O2-->4SiO2+3H2O
C7H6O2+15/2O2-->7CO2+3H2O
2FeS2+11/2O2-->Fe2O3+4SO2
I4O9-->I2O6+I2+3/2O2

i HOPE THIS HELPS.:)

Answer 4

2Na + 2H20 === 2NaOH + H2
4Si2H3 + 11O2 === 8SiO2 + 6H2
wait until i'm back