Question

1. Paul has test results of a sooty flame when burned and a positive reaction to sulfuric acid. He states that his unknown is hexane. What was wrong about his conclusion?

2. Alkanes find many commerical uses. Give at least 3 commercial uses for alkanes and name one alkane that is used as you described.

3. Which classes of compounds cannot perform addition reactions?

Answer 1

Ans 1 :

The unsaturated hydrocarbons burn with sooty flame as they have more number of carbon atoms than the amount of hydrogen atoms in the compound and also they have stronger intramolecular bonds in them , due to which they are subjected to incomplete combustion.

Whereas the saturated hydrocarbons have weaker single bonds and sufficient number of hydrogen atoms in their compounds , due to which they give clear flames on burning in the presence of oxygen.

Hexane is a saturated hydrocarbon , with sufficient number of hydrogen atoms , due to which it must give clear ( and not sooty ) flame.