How would I go about writing an Excellence answer for Question 3 in the 2019 exam paper?
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There are two parts to question 3 in the 2019 paper.
Part a has one excellence opportunity. You need to correctly fill in the table about litmus paper and baking soda. To get excellence you need to explain WHY you get the results, for example stating the sodium hydroxide turns red litmus paper blue because it is a base. HCl and red litmus paper shows no colour change so you’d need to confirm using baking soda. The baking soda and the HCl will create a neutralisation reaction, which produces carbon dioxide, you would observe bubbles forming/hear fizzing. Adding red litmus to sodium chloride will have no colour change and there will be no reaction between sodium chloride and baking soda because sodium chloride is a neutral salt.
You need to explain how you identified all 3 of the solutions.
In Part B the excellence from from the second half of the question. The equation is already balanced, so you can only get Merit from this correct symbol equation.
To get Excellence you need to explain how we would know the reaction between copper carbonate and sulfuric acid is finished. Because carbon dioxide gas is released in this neutralisation reaction, once no more gas is being released, you can assume the reactants have all been used up. You could check this by adding universal indicator and once the reaction is complete the solution should be neutral so the U.I. would show green, pH 7.
You MUST also talk about how you would get copper sulfate crystals for Excellence. The solution left over from the reaction will contain copper sulfate and water (the carbon dioxide will have been released into the air). To remove the water, you just need to add heat to evaporate it. This will leave behind solid blue copper sulfate crystals.
I hope this makes sense and helps you get a solid Excellence grade.
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