Topic 9

Question 1

Why is ethanol added to a test tube contained halogenoalkanes and silver nitrate

Answer 1

To make the halogenoalkane soluble

Question 2

Explain why halide ions are present in a mixture containing a halogenoalkane which only has covalent bonds

Answer 2

• The halogenoalkane is hydrolysed by the water
• C-H bond breaks heterolytically producing ions

Question 3

Describe the processes that occur on the surface of a heterogeneous catalyst during the oxidation of ammonia in air

Answer 3

• Reactants absorb onto catalyst
• there are active sites on the catalyst surface
• bonds in the reactants are weakened and or broken

Question 4

What is meant by the term ‘standard enthalpy change of combustion’

Answer 4

It is the enthalpy change when one mole of a substance burns completely in oxygen under standard conditions of 100 KPa

Question 5

What effect does a catalyst have on the Maxwell-Boltzmann distribution curve

Answer 5

A catalyst would have no effect

Question 6

How would you draw the maxwell-boltzmann distribution curve for a system with a higher temperature

Answer 6

The peak would be moved to the right and it would be lower down, more molecules would have greater energy than the Ea line

Question 7

Explain why a small increase in temperature results in a large increase in the rate of gaseous reactions

Answer 7

• higher temperature gives molecules more kinetic energy
• as the molecules have higher kinetic energy there is higher collision frequency
• more molecules have an energy greater than the activation energy
• so a greater proportion of the collisions result in a reaction