(c) The student wrote about how the copper sulphate was made. "Some of the acid was warmed. Copper oxide was added. The mixture was stirred. More copper oxide was added until no more would react. The mixture was then filtered." (i) Why was the acid warmed? (ii) Copper oxide was added until no more a would react. Explain why. (iii) The filtration apparatus is shown. Describe and explain what happens as the mixture is filtered. __ (1) (2) x

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(c) The student wrote about how the copper sulphate was made. "Some of the acid was warmed. Copper oxide was added. The mixture was stirred. More copper oxide was added until no more would react. The mixture was then filtered." (i) Why was the acid warmed? (ii) Copper oxide was added until no more a would react. Explain why. (iii) The filtration apparatus is shown. Describe and explain what happens as the mixture is filtered. __ (1) (2) x

Answer 1

The acid was warmed to increase the rate of reaction with copper oxide. (ii) 【Explanation】: In producing copper sulphate, copper oxide was added until no more would react with the acid. The reason is to ensure that all the acid reacts. When all of the acid has reacted, adding additional copper oxide will not lead to further reaction because there is no acid left to react with; this is also known as the "limiting reagent." 【Answer】: Copper oxide was added until no more would react in order to ensure that all the acid reacts. (iii) 【Explanation】: Filtration is a separation technique used in instances like obtaining a pure copper sulphate solution. During filtration, the mixture of unreacted substances - say unreacted copper oxide and the copper sulphate solution will be moved through a filter. Filtration exploits the size difference between the crystal entities of copper oxide particles and solution of copper sulphate. The smaller molecules of the copper sulphate solution easily pass through the fine pores of the filter, however, larger unreacted copper oxide particles cannot pass due it’s the size and will be left as residue, thus separated. 【Answer】: As the mixture is filtered, the fine particles of the copper sulphate solution and the larger unreacted copper oxide particles are separated, with the copper sulphate solution passing through and the unreacted copper oxide remaining as a residue on the filter.

Answer 2

Warming of the acid is a common procedure during the preparation of copper sulphate in order to speed up the reaction. The increase in temperature increases the energy of the acid particles causing them to move faster. This increase in movement signifies that acid particles collide with copper oxide more frequently and with greater force, enhancing the overall rate of reaction.

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