What is the effect of a high activation energy on a chemical reaction?
a. it reduced the potential energy of the reactants.

b. it reduces the potential energy of the products
.
c. it makes the reaction produce more energy.

d. it makes the reaction harder to start.

e. it makes the reaction endothermic.

option D= it makes the reaction harder to start.

Explanation:

Activation energy:

It is the minimum amount of energy required by chemical specie to start the chemical reaction.

Explanation:

The activation energy is inversely related to the rate of reaction. The higher the activation energy the slower will be the reaction rate.

Molecules are colloid with each other and gain kinetic energy if this energy is higher than the transition state energy then molecules easily undergo the chemical reaction. Because molecules easily overcome the barrier i.e transition state.

When the kinetic energy is lower than molecules can not pass the barrier. They require the input which is called activation energy to pass the barrier.

The higher the activation energy, the difficult for the reaction to proceed. Catalyst are used to lower the activation energies because in this way lower will be the transition state, and higher will be the reaction rate.

it is a solid

explanation:

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.