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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
To find the mass of the empty test tube, subtract the mass of the contents from the total mass when hydrated cobalt chloride was added. From the provided data:
Mass of test tube and contents at initial (0 sec) = 26.5 g Mass of test tube and contents after heating (120 sec) = 25.6 g
Mass of empty test tube = Mass at 0 sec - Mass after heating = 26.5 g - 2.0 g = 24.5 g
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 process. When hydrated cobalt chloride is heated, it loses water as it converts into anhydrous cobalt chloride. This loss of water contributes to the overall decrease in 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 hydrated cobalt chloride had been converted to anhydrous cobalt chloride, and no more water vapor was being released.
Step 4
Calculate the energy taken in during this reaction.
Answer
To calculate the energy taken in during the reaction, use the formula:
a) Energy = (mass / molar mass) × energy per mole
Where:
- Mass of hydrated cobalt chloride = 2.00 g
- Molar mass of hydrated cobalt chloride = 238 g/mol
- Energy per mole = 88.1 kJ
Calculating:
a) Energy = (2.00 g / 238 g/mol) × 88.1 kJ = 0.740 kJ
Therefore, the energy taken in during this reaction is 0.740 kJ.
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. This type of reaction absorbs energy from the surroundings, leading to the decomposition of hydrated cobalt chloride into anhydrous cobalt chloride and water.