Question

Liquid petrol does not ignite spontaneously when exposed to the air because
(A)The ΔH for the combustion of petrol is positive
(B) Reaction between petrol and oxygen requires a catalyst
(C) The reactants are in different physical states
(D) Not enough molecules possess sufficient energy to react

Answer 1

A cant be bcoz combustion of petrol gaives deltaH is as -ve
c option is reactant are in different phase doesn't make any sense bcoz water and Sodium metal reacts spontaneously even they are in different phases...

confusing B and D
i can say for a spark as a catalyst or for a matchstick as catalyst
but is it worthwhile to say them as catalyst...?
once spark is supplied for them, there is no need of spark :)
Here both of these materials start the reaction but according to the definition of catalyst
it only alters the rate of reaction mean increases the rate of reaction..
so the D will be better option

Answer 2

D is the answer B is not because catalyst is a substance that speeds up a reaction by lowering the activation energy since no catalyst are used in this reaction so D is the answer and @chmvijay spark or match stick provide the activation energy for the reaction not lower it so they are not catalysts

Answer 3

yaaa :)