Question

How do you balance
C2H2 + O2 -> CO2 + H2O??

Is it C2H2 + 5/2 O2 -> 2CO2 + H2O
or 2C2H2 + 5O2 -> 4CO2 + 2H2O ?

Answer 1

Both are correct and equivalent

The second is the first multiplied by 2, then both of them have the same relation (proportion) for every reactant and product.