How would you balance the following chemical equation: . c2h2+> co2+h2o

C2H2 + 1.5O2 ===> 2CO2 + H2O

1. look at the No. of carbons in the hydrocarbon (C2H2) that is the number of CO2's formed

2. look at the No. of hydrogen's in the hydrocarbon, divide by two and the answer is the number of water molecules formed 

3. count all the oxygens on the right and balance it on the left you can have halfs 

hope that helps

Balance the number of each element on both sides of the chemical reaction. We may start off with Carbon. Multiply the compound CO2 by 2. By this the number of oxygen on the right hand side of the chemical reaction is now 5. Multiply the O2 by 5/2. The chemical reaction becomes
                               C2H2 + (5/2)O2 > 2CO2 + H2O
To eliminate the fraction, multiple the whole chemical reaction by 2 to give the final answer of,
                               2C2H2 + 5O2 ---> 4CO2 + 2H2O

It is a body of knowledge gained  using  inquiry and experimentation