The diagram shows a molecular model used to compare propane fuel with ammonia in a portable refrigeration unit. Black atoms are carbon, white atoms are hydr...
Question 1 Report
The diagram shows a molecular model used to compare propane fuel with ammonia in a portable refrigeration unit. Black atoms are carbon, white atoms are hydrogen and the atom marked N is nitrogen.
(a) Name the element represented by the black atoms. [1]
(b) Give the formula of propane. [1]
(c) Suggest why propane and ammonia are both simple molecular substances. [3]
Fig. 1 shows a section through a car tyre made from vulcanised rubber. Sulfur links join long hydrocarbon chains. Engineers test the tyre material before fitting it to a vehicle.
(a) Name the element present in the chains as well as hydrogen. [1]
(b) Give the name of the process that adds sulfur cross-links to rubber. [1]
(c) Suggest two effects of cross-links on the tyre material. [3]
Answer Details
Propane and ammonia
(a) The black atoms represent carbon. [1 mark]
(b) Propane has three carbon atoms and eight hydrogen atoms, so its formula is \(\mathrm{C_3H_8}\). [1 mark]
(c) Both substances are simple molecular because they consist of separate molecules. The atoms within each molecule are joined by covalent bonds, but there are only weak forces between molecules. [3 marks]
Vulcanised rubber
(a) The chains contain carbon as well as hydrogen. [1 mark]
(b) Adding sulfur cross-links to rubber is called vulcanisation. [1 mark]
(c) Sulfur cross-links tie the long chains together. This makes the rubber stronger and less likely to stretch permanently. Cross-links can also improve resistance to heat or wear. Any two valid effects gain credit. [3 marks]
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