Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Organic Chemistry
785 practice questions
Topics covered
Practice questions
91–100 of 335 · Normal
Question 91
3 marks · Normal
Answer and see the solution →The boiling points of fractions from crude oil are related to the number of carbon atoms in their molecules.
Boiling points of two hydrocarbon fractions Fraction Typical Number of Carbon Atoms Boiling Point (°C) Gasoline (petrol) 8 110 Diesel 15 260 (a)[3 marks]Calculate the increase in boiling point per additional carbon atom between these two fractions.
Question 92
3 marks · Normal
Answer and see the solution →Explain why hydrocarbons with larger molecules burn less easily than hydrocarbons with smaller molecules.
Question 93
4 marks · Normal
Answer and see the solution →The table below shows properties of different hydrocarbon fractions obtained from crude oil.
Properties of hydrocarbon fractions Fraction Approx. number of C atoms Boiling point (°C) Colour Flow (viscosity) Ease of burning Refinery gas 3 -20 Colourless Very runny Burns very easily Kerosene 12 200 Light yellow Fairly runny Burns easily Fuel oil 20 340 Dark brown Thick Does not burn easily (a)[2 marks]Which fraction is the most viscous? Give a reason for your answer.
(b)[2 marks]State how boiling point, colour, and ease of burning change as you go from refinery gas to fuel oil.
Question 94
1 mark · Normal
Answer and check →Which statement about hydrocarbon fractions with small molecules is correct?
- A.They have high boiling points and are very viscous.
- B.They are dark in colour and burn with difficulty.
- C.They are very volatile and burn easily.
- D.They are thick liquids and flow slowly.
Question 95
2 marks · Normal
Answer and see the solution →State two ways in which refinery gas differs in physical properties from bitumen, another fraction from crude oil.
Question 96
4 marks · Normal
Answer and see the solution →Hydrocarbon fractions are collected at different heights in a fractionating column, depending on their boiling points.
(a)[1 mark]State what is meant by the volatility of a liquid.
(b)[2 marks]Explain why the fraction collected at the top of the column is more volatile than the one at the bottom.
(c)[1 mark]Give one use each for the top fraction and the bottom fraction.
Question 97
2 marks · Normal
Answer and see the solution →State the name of the process used to separate crude oil into useful fractions and give one reason why crude oil must be separated in this way.
Question 98
4 marks · Normal
Answer and see the solution →This question is about combustion of hydrocarbons.
(a)[1 mark]Write the word equation for the complete combustion of propane.
(b)[1 mark]State the two main products formed during complete combustion of a hydrocarbon.
(c)[2 marks]Explain, using your knowledge of incomplete combustion, why burning a hydrocarbon in a limited supply of air may produce a dangerous gas.
Question 99
3 marks · Normal
Answer and see the solution →Explain why burning hydrocarbons in a poorly ventilated room can lead to serious health risks. In your answer, refer to the products formed during incomplete combustion.
Question 100
4 marks · Normal
Answer and see the solution →The table below shows information about some fractions obtained from crude oil.
Fractions from crude oil Fraction Approximate Boiling Point (°C) Main Use Refinery gas < 40 Bottled gas Gasoline 40–100 Fuel for cars Diesel oil 250–350 Fuel for lorries Bitumen > 350 Road surfacing (a)[1 mark]Identify the fraction with the lowest boiling point and state its main use.
(b)[2 marks]Which fraction is most likely to contain the largest hydrocarbon molecules? Explain your answer using data from the table.
(c)[1 mark]Suggest why bitumen is not used as a fuel.