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A student investigated the change in mass when hydrated cobalt chloride was heated - AQA - GCSE Chemistry - Question 2 - 2022 - Paper 2
Question 2
A student investigated the change in mass when hydrated cobalt chloride was heated. The word equation for the reaction is: hydrated cobalt chloride ⇌ anhydrous cob... show full transcript
Worked Solution & Example Answer:A student investigated the change in mass when hydrated cobalt chloride was heated - AQA - GCSE Chemistry - Question 2 - 2022 - Paper 2
Step 1
Determine the mass of the empty test tube.
Answer
The mass of the empty test tube can be calculated by subtracting the mass of the hydrated cobalt chloride and the final mass after heating from the initial mass of the test tube and contents. From the data, the initial mass with contents (2.0 g of hydrated cobalt chloride) is 26.5 g. After heating, the final mass is 25.6 g. Thus, the mass of the empty test tube is:
Step 2
Explain why the mass of the test tube and contents decreased.
Answer
The mass of the test tube and contents decreased because water vapor was produced during the heating of hydrated cobalt chloride. As the hydrated form is heated, it loses water in the form of steam, which escapes into the air, resulting in a net loss of mass.
Step 3
Suggest why the test tube and contents were heated until the mass did not change.
Answer
The test tube and contents were heated until the mass did not change to ensure that the reaction was complete. This indicates that all the water has evaporated, and no further mass loss occurs, confirming that the anhydrous form of cobalt chloride has been reached.
Step 4
Step 5
What type of reaction takes place when hydrated cobalt chloride is heated?
Answer
The reaction that takes place when hydrated cobalt chloride is heated is an endothermic reaction. In this process, energy is absorbed from the surroundings to facilitate the transformation from the hydrated to the anhydrous form.