Write the condensed formula of a linear alkane, whose molecular formula is C20H42 .

Linear alkanes can be written in condensed form using the following formula: CH3(CH2)nCH3 , where n is the number of CH2 the molecule has. The molecular formula of the problem has 20 carbons, two of them are for methyls, therefore, the condensed formula will have 18 CH2 .

Condensed formula: CH3(CH2)18CH3