A Level Official Exam Material
FREE Past paper Questions by Topic
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Unit 2: Energetics, Group Chemistry, Halogenoalkanes And Alcohols
Topic 7: Intermolecular forces
For both AS and A Level students
Q1. This question is about some aspects of the chemistry of iodine and its compounds.
In industry, the main source of iodine is sodium iodate(V), NaIO3, which occurs in deposits found in Chile.
In the human body, iodide ions, I– , are needed for the thyroid gland to function properly.
In many countries, potassium iodide, KI, is added to table salt as a source of iodide ions.
(d) (i) When chlorine is passed over iodine crystals, iodine monochloride, ICl, is formed. Iodine monochloride, ICl, is a liquid at room temperature whereas chlorine, Cl2, is a gas.
Explain, in terms of intermolecular forces, why this is so. (4) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 4 mark)
Q2. Which of the following compounds has the highest boiling temperature? Mr = relative molecular mass
A cyclopentane Mr = 70
B pentane Mr = 72
C butan-1-ol Mr = 74
D ethane-1,2-diol Mr = 62
(Total for question = 1 mark)
Q3. As Group 7 is descended, the boiling temperatures of the hydrogen halides, from HF to HI,
A decrease then increase.
B decrease.
C increase then decrease.
D increase.
(Total for question = 1 mark)
Q4. Sunflower oil is an important edible oil.
It can be used as an alternative to butter in cooking.
A useful method of comparing fats and oils is by measuring their iodine values.
An iodine value is the amount of iodine in grams that reacts with 100 g of a fat or oil.
The iodine value is a measure of the degree of unsaturation of the fat or oil.
(a) Trichloromethane and 1,1,1-trichloroethane are two possible solvents for this reaction.
(i) Give the skeletal formulae for trichloromethane and 1,1,1-trichloroethane . (2)
Trichloromethane 1,1,1-trichloroethane
(ii) Explain why 1,1,1-trichloroethane has a higher boiling temperature than trichloromethane. (2)
............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(iii) Suggest why solvents such as trichloromethane and 1,1,1-trichloroethane are no longer used. (1) ............................................................................................................................................. .............................................................................................................................................
(Total for question = 5 marks)
Q5. This is a question about alcohols.
(a) (i) The distillation apparatus effectively separates ethanal from ethanol because of the large difference in boiling temperatures, which is a result of the hydrogen bonding between the molecules in ethanol.
Draw a hydrogen bond between two ethanol molecules.
Clearly indicate any relevant dipoles and lone pairs of electrons.
Label the bond angle about the hydrogen involved in the hydrogen bond and give its value. (3)
(ii) Explain why hydrogen bonds do not form between ethanal molecules. (1) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 4 marks)
Q6
Graphite and the hexagonal boron nitride are both used as lubricants because of the weak intermolecular forces between the layers of hexagonal rings. Identify these intermolecular forces and describe how they arise. (3) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 3 marks)
Q7. In water, hexan-1-ol is less soluble than ethanol.
The best explanation for this is that
A hexan-1-ol molecules cannot form hydrogen bonds with water molecules but ethanol molecules can.
B carbon-carbon bonds are stronger in hexan-1-ol than in ethanol.
C London forces between hexan-1-ol molecules are stronger than between ethanol molecules.
D permanent dipole forces are stronger in hexan-1-ol than in ethanol.
(Total for question = 1 mark)
Q8. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which of these isomers with the formula C8H18 has the lowest boiling temperature?
A CH3CH(CH3)CH2CH2CH(CH3)CH3
B CH3CH(CH3)CH2CH2CH2CH2CH3
C CH3C(CH3)2CH2CH(CH3)CH3
D CH3CH2CH2CH2CH2CH2CH2CH3
(Total for question = 1 mark)
Q9. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which of these compounds would be expected to have the highest boiling temperature?
A (CH3)3COH
B CH3CH2CH2CH2OH
C CH3CH2CH(CH3)2
D CH3CH2CH2CH2CH3
Use this space for any rough working.
Anything you write in this space will gain no credit.
(Total for question = 1 mark)
Q10. Which statement is not explained by hydrogen bonding? (1)
A all Group 1 hydroxides are soluble in water
B many simple alcohols are soluble in water
C the density of ice is less than the density of liquid water at 0 °C
D the melting temperature of water is abnormally high
(Total for question = 1 mark)
Q11. Answer the questions with a cross in the boxes you think are correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
This question is about hydrogen bonding.
(a) Which property is not due to hydrogen bonding? (1)
A ice has a lower density than water at 0°C
B hydrogen fluoride has a higher boiling temperature than hydrogen chloride
C H—H bond enthalpy is greater than Si—H bond enthalpy
D alcohols are less volatile than alkanes with a similar molar mass
(b) Which diagram best represents a hydrogen bond between two water molecules? (1)
Q12. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which of these pure compounds has hydrogen bonding in the liquid state?
A 1,1,1-trichloroethane, CH3CCl3
B trimethylamine, (CH3)3N
C hydrogen fluoride, HF
D hydrogen sulfide, H2S
(Total for question = 1 mark)
Q13. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which intermolecular forces exist between the molecules of the compound shown?
A hydrogen bonding and London forces only
B hydrogen bonding and permanent dipole-permanent dipole forces only
C London forces and permanent dipole-permanent dipole forces only
D hydrogen bonding, permanent dipole-permanent dipole forces and London forces
(Total for question = 1 mark)
Q14. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which is not correct about ice?
A ice has a lower density than water
B H2O molecules are further apart in ice than in water
C the H—O—H bond angle is the same in ice and in water
D H2O molecules in ice are held together by hydrogen bonds
(Total for question = 1 mark)
Q15. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which solvent dissolves the greatest amount of hydrocarbon C35H72?
A butan-1-ol
B ethanoic acid
C hexane
D water
(Total for question = 1 mark)
Q16. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which of the following statements about water is not due to hydrogen bonding?
A water has a less open structure than ice
B ice cubes float in a glass of iced water
C when water freezes its volume increases
D water is a good solvent for ionic compounds
(Total for question = 1 mark)
Q17. This question is about ethanol and bioethanol.
The main fuel used as a petrol substitute is bioethanol.
Bioethanol is ethanol that has been produced by fermentation.
The starting material is usually some form of plant material rich in starch, such as wheat, maize or potatoes.
Enzymes in yeast convert this material to simple carbohydrates such as glucose (C6H12O6) and then to ethanol and carbon dioxide.
C6H12O6 → 2CH3CH2OH + 2CO2
The mixture is left for several days until fermentation is complete.
The percentage of ethanol is never greater than 15 % because higher concentrations of ethanol kill the yeast.
A common blend of fuel is 95 % petrol and 5 % bioethanol.
The engine does not need to be modified for this mixture.
(a) Give one advantage and one disadvantage of using bioethanol in petrol. (2)
Advantage ............................................................................................................................................. .............................................................................................................................................
Disadvantage ............................................................................................................................................. .............................................................................................................................................
(d) Ethanol is hygroscopic, which means it readily absorbs water from the air.
(i) Give a possible reason why ethanol is able to absorb water. (1) ............................................................................................................................................. .............................................................................................................................................
(ii) Suggest a problem arising from the hygroscopic nature of ethanol when using this fuel in a motor vehicle. (1) ............................................................................................................................................. .............................................................................................................................................
(Total for question = 4 marks)
Q18. This question is about halogenoalkanes. (c) The boiling temperatures of some halogenoalkanes are shown.
Explain the trend in boiling temperature of these halogenoalkanes by comparing the intermolecular forces involved. Detailed explanations of the forces involved are not required. (4) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 4 marks)
Q19. This question is about compounds containing Group 2 elements.
(b) Magnesium carbonate, MgCO3, is a white solid used as an additive in foods.
(i) Explain, in terms of energy changes, why magnesium carbonate is insoluble in water. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 2 marks)
Q20. Ethanol can be made in industry by the reaction of ethene with steam, using a phosphoric(V) acid catalyst. CH2=CH2(g) + H2O(g) CH3CH2OH(g)
ΔrH = −45 kJ mol−1
The reaction is carried out at 300°C and 60 atm.
An initial yield of 5 % is achieved when the ethene and steam first pass through the reactor.
(b) The product of the reaction is a mixture of ethanol and water.
Explain why ethanol and water mix together fully.
You may find it helpful to draw a diagram. (3) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 3 marks)
Q21. This question is about the halogens and some of their compounds.
(d) The graph shows the boiling temperatures of the hydrogen halides.
Explain the trend in the boiling temperatures of the hydrogen halides. (4) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 4 marks)
If you need the markscheme, including the examiners' reports for each question, and more exam and teaching materials on this topic, contact me through the contact page