Question

What is the relationship between the number of carbon atoms in hydrocarbon at its boiling point ?

Answer 1

• If no of carbon atoms be C
• Boiling point of compound be BP

So

$\\ \tt\longmapsto C\propto BP$

• No of carbon atoms is directly proportional to the boiling point of the compound.
• If no of carbon atoms increases in a hydrocarbon the length of carbon chain also increases and all carbons get wrapped around themselves.
• Which causes increase in boiling point of compound.

Look the table below for the boiling points of some alkanes

$\boxed{\begin{array}{c|c}\boxed{\bf Alkane}&\boxed{\bf Boiling point}\\ \sf CH_4&\sf -164°C \\ \sf C_2H_6 &\sf -88.6°C \\ \sf C_3H_8&\sf 42.1°C \\ \sf C_4H_{10} &\sf -0.5°C \\ \sf C_5H_{12} &\sf 36.1°C \\ \sf C_6H_{14} &\sf 68.9°C \\ \sf C_7H_{16} &\sf 98.4°C \\ \sf C_8H_{18} &\sf 125.7°C \\ \sf C_9H_{20} &\sf 150.4°C \\ \sf C_{10}H_{22} &\sf 150.7°C \end{array}}$