2010 Chemical, Energy and Resources Jan

Question 1

Name the process used to obtain kerosene crude oil and explain why the process works

Answer 1

• Fractional distillation 

* Because fractions have different boiling points

Question 2

Explain why straight chain isomers have a higher boiling point than branched chain isomers

Answer 2

• Branched chains have less surface contact

* Branched chains have fewer London Forces

Question 3

Explain why the straight isomer is converted by the petroleum industry to a branched chain isomer

Answer 3

• Branched chains have more efficient combustion

Question 4

Describe and explain how the concentration of ozone is maintained in the stratosphere

Answer 4

• O + O2  O3
• The reaction is reversible
• Rate of formation of ozone is the same as rate of
decomposition

Question 5

2H2O2  2H2O + O2

Explain why increasing the concentration of H2O2 increases the rate of decomposition

Answer 5

• More crowded particles

* More frequent collisions

Question 6

Explain how a catalyst can increases the rate of decomposition of H2O2

Answer 6

• Reaction takes alternative route
• Activation energy is lowered
• More molecules have energy above activation energy

Question 7

Explain using a Boltzmann diagram why increasing the temperature increases the rate of reaction

Answer 7

• More molecules have energy above activation energy

Question 8

Explain the advantages of the manufacture of H2O2 from hydrogen and oxygen

Answer 8

• Oxygen comes from ai
• No poisonous materials formed
• No waste products formed

Question 9

Suggest two reasons why standard enthalphy changes of combustion determined experimentally are less exothermic than calculated theoretical values

Answer 9

• Bond breaking absorbs energy
AND bond making releases energy
• More energy released than absorbed

Question 10

Name the catalyst in this reaction

C2H4 + H20 -> C2H5OH ∆T=-49

Answer 10

• H3PO4 acid

Question 11

State le Chateliers principle

Answer 11

• The position of equilibrium will shift so as to minimise the effect of any change in conditions

Question 12

Using le Chateliers principle explain the conditions that would give the maximum equilibrium yield

C2H4 + H20 -> C2H5OH ∆T=-49

Answer 12

• Low temperature AND high pressure
• Low temperature because the (forward) reaction is
exothermic
• High pressure because there are fewer moles (of gas) on the right hand side

Question 13

Describe two ways in which chemists can reduce the damage to the environment

Answer 13

• Develop photodegradable polymers
• Develop biodegradable polymer
• Designing processes with high atom economy/ Develop ways of sorting AND recycling polymers

Question 14

Explain why ethan-1,2-diol is very souluble in water

Answer 14

• Has hydroxyl (groups)

* Forms hydrogen bonds with water

Question 15

What type of raditaion is absorbed by methane molecules and what effect does this radiation have on these molecules

Answer 15

• Infrared (radiation absorbed) 

* By (C–H) bond vibration