Question

Give the molecular formula of a hydrocarbon containing five carbon atoms that is (a) an alkane, (b) a cycloalkane, (c) an alkene, (d) an alkyne. Which are saturated and which are unsaturated hydrocarbons?

Short answer

The molecular formulas are: (a) Alkane: C5H12 (saturated), (b) Cycloalkane: C5H10 (saturated), (c) Alkene: C5H10 (unsaturated), and (d) Alkyne: C5H8 (unsaturated).

Step-by-step solution

(a) Alkane Formula

An alkane is a hydrocarbon containing only single bonds between carbon atoms. The general formula for an alkane is CnH2n+2, where n is the number of carbon atoms. To find an alkane with five carbon atoms, plug n = 5 into the formula: C5H(2*5)+2 = C5H12.

(b) Cycloalkane Formula

A cycloalkane is a hydrocarbon in which the carbon atoms form a closed loop or cycle. The general formula for a cycloalkane is CnH2n, where n is the number of carbon atoms. To find a cycloalkane with five carbon atoms, plug n = 5 into the formula: C5H(2*5) = C5H10.

(c) Alkene Formula

An alkene is a hydrocarbon containing a carbon-carbon double bond. The general formula for an alkene is CnH2n, where n is the number of carbon atoms. To find an alkene with five carbon atoms, plug n = 5 into the formula: C5H(2*5) = C5H10.

(d) Alkyne Formula

An alkyne is a hydrocarbon containing a carbon-carbon triple bond. The general formula for an alkyne is CnH2n-2, where n is the number of carbon atoms. To find an alkyne with five carbon atoms, plug n = 5 into the formula: C5H(2*5)-2 = C5H8.

Saturated and Unsaturated Hydrocarbons

Saturated hydrocarbons have single bonds between all of their carbon atoms, which means they have the maximum number of hydrogen atoms possible. Unsaturated hydrocarbons have one or more carbon-carbon double or triple bonds, which means they have fewer hydrogen atoms than the corresponding saturated hydrocarbon. The alkane (C5H12) and the cycloalkane (C5H10) are both saturated hydrocarbons because they consist of single bonds between the carbon atoms. The alkene (C5H10) and the alkyne (C5H8) are unsaturated hydrocarbons. The alkene has a double bond and the alkyne has a triple bond, which means that they both have fewer hydrogen atoms than the corresponding saturated hydrocarbon.