Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Organic Chemistry
785 practice questions
Topics covered
Practice questions
151–160 of 335 · Normal
Question 151
3 marks · Normal
Answer and see the solution →An alkene has 8 carbon atoms in its molecule.
Calculate the number of hydrogen atoms present in one molecule of this alkene. Show your working.
Question 152
3 marks · Normal
Answer and see the solution →Alkenes are described as unsaturated hydrocarbons.
Explain what 'unsaturated' means and how you can test for unsaturation using a chemical reaction.
Question 153
4 marks · Normal
Answer and see the solution →A student compares the combustion reactions of three alkenes. The table shows the number of carbon and hydrogen atoms in each.
Alkene Number of carbon atoms (n) Number of hydrogen atoms Ethene 2 4 Propene 3 6 Pentene 5 10 (a)[1 mark]State the general formula for alkenes.
(b)[2 marks]Explain the pattern between the number of carbon atoms and hydrogen atoms in these alkenes.
(c)[1 mark]Write the molecular formula for hexene.
Question 154
1 mark · Normal
Answer and check →Which statement best describes an addition reaction of ethene?
- A.Two ethene molecules join together to form a longer chain.
- B.Ethene reacts with oxygen to form carbon dioxide and water.
- C.Bromine atoms add across the double bond of ethene.
- D.Hydrogen atoms are lost from ethene forming ethyne.
Question 155
4 marks · Normal
Answer and see the solution →This question is about reactions of propene (C3H6).
(a)[1 mark]Explain why propene is classified as an unsaturated hydrocarbon.
(b)[1 mark]Write a word equation for the addition reaction of propene with hydrogen.
(c)[2 marks]Describe what is formed when propene burns in a plentiful supply of air.
Question 156
2 marks · Normal
Answer and see the solution →Alkenes are a family of unsaturated hydrocarbons that undergo two main types of chemical reactions: combustion and addition.
Describe what happens during:
(a)[1 mark](i) the combustion of an alkene in oxygen
(b)[1 mark](ii) an addition reaction of an alkene
Question 157
2 marks · Normal
Answer and see the solution →State the overall type of reaction that occurs when bromine water reacts with ethene, and give the name of the organic product formed.
Question 158
4 marks · Normal
Answer and see the solution →(a)[1 mark]Describe the result you would see when bromine water is shaken with a liquid alkene.
(b)[1 mark]Describe what you would see if bromine water is shaken with a liquid alkane, under the same conditions.
(c)[2 marks]Explain how you can use this test to distinguish between an alkene and an alkane.
Question 159
3 marks · Normal
Answer and see the solution →A student wants to test whether an unknown colourless liquid is an alkane or an alkene. The student adds a few drops of bromine water to the liquid in a test tube and shakes it. After a short time, the orange colour disappears and the mixture becomes colourless. Explain what conclusion the student should make about the liquid and the reason for this result.
Question 160
4 marks · Normal
Answer and see the solution →A student investigates the reaction between different alkenes and bromine water. The table shows the results.
Observations on addition of bromine water to different compounds. Compound Observation after adding bromine water Ethene Colourless Propene Colourless Butane Orange Cyclohexene Colourless (a)[2 marks]Which of these compounds are alkenes? Give a reason for your choice.
(b)[2 marks]Write a balanced equation for the reaction of ethene with bromine water.