Question 1

What is the general equation for complete combustion of an alkane?

Accepted Answer

For an alkane with formula CnH2n+2, complete combustion follows CnH2n+2 + (3n+1)/2 O2 → nCO2 + (n+1)H2O. The reaction is exothermic, and the normal flame is blue.

Question 2

How much oxygen is required for complete combustion of butane?

Accepted Answer

One C4H10 molecule requires 6.5 O2 molecules, equivalent to 13 oxygen atoms. The balanced integer equation uses two butane molecules, so it requires 13 O2 molecules in total: 2 C4H10 + 13 O2 → 8 CO2 + 10 H2O.

Question 3

What products form during incomplete combustion of an alkane?

Accepted Answer

When oxygen supply is limited, incomplete combustion can produce carbon monoxide, and with very limited oxygen it can also produce elemental carbon, commonly called soot. The exact product ratio depends on oxygen availability.

Question 4

Why are butane and 2-methylpropane structural isomers?

Accepted Answer

Both molecules have the formula C4H10, but their atom connectivity differs. Butane has four carbon atoms in one unbranched chain, while 2-methylpropane has three carbon atoms in its main chain with a methyl branch at carbon 2.

Question 5

Are butane and 2-methylpropane conformers?

Accepted Answer

No. Conformers arise by rotation around bonds without changing atom connectivity. Butane and 2-methylpropane differ in carbon-chain connectivity, so they are structural isomers rather than conformers.

Combustion & Isomerisation of Alkanes

About this lab

Practice