Pentane gas (c5h12) combusts with oxygen gas (o2) to form water (h2o) and carbon dioxide (co2).
write a balanced chemical equation for this reaction and explain the scientific principle (statement) that requires the balancing of an equation to make it conform to reality.

First we write the reactants and the products in this manner shown below: 

C5H12 + O2 = H20 + CO2 

This equation is not yet balanced so we add coefficients to make the equation balance: 

C5H12 + 8O2 = 6H20 + 5CO2 

The principle of concern here is the Law of Conservation of Mass. 

This law states that for a system that is isolated, the mass is not created nor destroyed. Hence for this system, the amount of CO2 and water created is exactly from the reactants pentane and oxygen. 
 

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