Q.Write the balanced equation for the complete combustion of propane, and give one example equation for the pyrolysis (cracking) of decane.

Complete combustion burns propane fully in excess oxygen to carbon dioxide and water, releasing heat: $\text{C}_3\text{H}_8+5\text{O}_2 \rightarrow 3\text{CO}_2+4\text{H}_2\text{O}+\text{heat}$ (balance carbons: 3 CO2; hydrogens: 8 H give 4 H2O; oxygens: $3(2)+4(1)=10$ O atoms $=5\ \text{O}_2$). Pyrolysis is a completely different process: heating decane strongly in the ABSENCE of air breaks its carbon skeleton into smaller fragments, e.g. $\text{C}_{10}\text{H}_{22} \xrightarrow{\Delta} \text{C}_5\text{H}_{12}+\text{C}_2\text{H}_4+\text{C}_3\text{H}_6$ (total carbon $5+2+3=10$ and total hydrogen $12+4+6=22$ both correctly balance against the decane reactant), a mixture of a smaller alkane and two alkenes -- this is the reaction used industria …

For combustion, balance C, then H, then O across the equation. For pyrolysis, choose any split of the carbon skeleton into fragments whose formulas are valid alk …

Forgetting that pyrolysis needs the ABSENCE of air/oxygen (unlike combustion, which needs excess oxygen); writing an unbalanced combustion equation by …