GCSE Edexcel Chemistry Measuring temperature change: A student investigated the react

Question

A student investigated the reaction between potassium iodide and lead nitrate.

(i) Solutions of potassium iodide and lead nitrate were mixed together.  
Lead iodide and potassium nitrate were formed.  
Complete the word equation.

_____________ + _____________ → _____________ + _____________

(ii) The student recorded the total mass of the reactants and the total mass of the products.  
The results are shown in Figure 4.

total mass in g   
reactants    products  
21.7            21.7

Figure 4

State how the results in Figure 4 show that mass is conserved in this reaction.

(b) In another experiment, a student investigated the temperature decrease when different amounts of ammonium nitrate crystals were dissolved in 100 cm³ of water.  
The apparatus used is shown in Figure 5.

Figure 5

The student used the following method.

step 1  pour 100 cm³ of water into the polystyrene cup  
step 2  add one spatula of ammonium nitrate crystals to the water  
step 3  stir the mixture  
step 4  use the thermometer to record the lowest temperature reached by the mixture  
step 5  repeat steps 1 to 4 using different amounts of ammonium nitrate

(i) Name a piece of apparatus that should be used to measure the 100 cm³ of water in step 1.

(ii) The student cannot work out the temperature decrease using the method described.  
State what the student must do before step 2 to be able to work out the temperature decrease.

(iii) State why a polystyrene cup is used in this experiment.

(iv) Figure 6 shows the reaction profile for this reaction.  
Use the words from the box to complete the labels on Figure 6.

A student investigated the reaction between potassium iodide and lead nitrate - Edexcel - GCSE Chemistry - Question 3 - 2020 - Paper 1

Worked Solution & Example Answer:A student investigated the reaction between potassium iodide and lead nitrate - Edexcel - GCSE Chemistry - Question 3 - 2020 - Paper 1

Complete the word equation.

State how the results in Figure 4 show that mass is conserved in this reaction.

Name a piece of apparatus that should be used to measure the 100 cm³ of water in step 1.

State what the student must do before step 2 to be able to work out the temperature decrease.

State why a polystyrene cup is used in this experiment.

Complete the labels on Figure 6.

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