O LevelChemistryCambridgeTopic Questions12. Experimental Techniques & Chemical Analysis12.1 Experimental Design

Experimental Design (Cambridge O Level Chemistry)

Topic Questions

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1a1 mark

The names of some pieces of equipment are shown.

stopwatch   balance    thermometer   gas syringe   burette   pipette

For each question, name the piece of apparatus that would be used in each case.

Each piece of equipment can be used once, more than once or not at all. 

Name the piece of apparatus that would be used to measure the time taken for a white precipitate to form when barium chloride is added to sodium sulfate.

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1b1 mark

Name the piece of apparatus that would be used to determine whether the reaction between magnesium and hydrochloric acid is exothermic.

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1c1 mark

Name the piece of apparatus that would be used to measure the volume of carbon dioxide produced when marble chips are added to hydrochloric acid.

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1d1 mark

Name the piece of apparatus used to add hydrochloric acid to 25 cm3 of sodium hydroxide solution during a titration.

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2a1 mark

A student investigated the effect of temperature on the mass of sodium chloride that dissolves in 100 cm3 of water. 

Name the piece of apparatus that would be used to measure the mass of sodium chloride.

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2b1 mark

A control variable is one which must be kept constant each time the investigation is repeated. 

Give one control variable in this investigation. 

The temperature of the water  
   
The volume of water  
   
The mass of sodium chloride  
   
The beaker used   

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2c4 marks

Complete these sentences using the word from the list.

solution saturated solute solvent
residue filtrate liquid



The salt is the .................................. because it dissolves in water. The water is the .................................. because it has the salt dissolved in it.

The mixture of salt and water is known as a ...................................

When no more salt can dissolve in water at a specific temperature, the solution has become..................................

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2d1 mark

The student used a thermometer to measure the temperature during their investigation.

Name a different piece of apparatus that would give the student a more precise reading. 

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3a1 mark

A student made copper sulfate crystals. 

The first two steps of their method are shown below. 

q6

 

Why should sulfuric acid be added in excess to copper carbonate?

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3b1 mark

The contents of the beaker in step 2 are separated using filtration. 


Identify the residue. 

Draw a circle around the correct answer.

 
water copper carbonate copper(II) sulfate sulfuric acid

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3c1 mark

Identify the filtrate. 

Draw a circle around the correct answer.

 
water copper carbonate copper(II) sulfate sulfuric acid
 

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3d2 marks

Describe how you would obtain dry copper(II) sulfate crystals from the solution. 

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1a3 marks

A student investigated the effect of the size of calcium carbonate lumps, CaCO3, on the rate of reaction with hydrochloric acid, HCl, using the following method:

  1. Put 50 cm3 of hydrochloric acid into a conical flask 
  2. Add 12 g of large calcium carbonate lumps into the flask
  3. Attach the gas syringe
  4. Measure the volume of gas produced every 30 seconds for 180 seconds 
  5. Repeat steps 1 - 4 using 12 g of small calcium carbonate lumps.
  6. The number of moles of gas for each volume was calculated.

The results for large calcium carbonate lumps are shown below.

Table 1

Time in seconds Number of moles of gas 
0 0.000
30 0.0012
60 0.0022
90 0.0030
120 0.0034
150 0.0037
180 0.0038


The student had already plotted the data for small calcium carbonate lumps.

  
Plot the data for the large calcium carbonate lumps and draw a line of best fit.

aqa-gcse-6-1h-tq5a-moles-of-gas-against-time-rates-graph

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1b
Sme Calculator4 marks

Determine the mean rate of reaction for small calcium carbonate lumps between 35 seconds and 90 seconds. 

Give the unit. 

Use the graph in part (a)

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1c2 marks

What conclusion can be made about the rate of reaction of small calcium carbonate lumps compared to large calcium carbonate lumps?

Give one reason for your answer. 

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1d
Sme Calculator2 marks

Complete and balance the equation for the reaction between calcium carbonate and hydrochloric acid.


_______   +   _______      →     CaCl2   +   _______    +    _______ 

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1e3 marks

State one advantage and two disadvantages of using a gas syringe as opposed to a upturned measuring cylinder when collecting gas.

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2a5 marks

A student investigated what happened when sodium thiosulphate dissolved in water.

   Experiment 1

By using a measuring cylinder, 20 cm3 of distilled water was poured into a polystyrene cup.
Use the thermometer diagram to record the temperature of the water in the table.

1 g of powdered sodium thiosulphate was added to the cup and the mixture stirred with a thermometer. Use the thermometer diagram to record the temperature of the solution.

   Experiment 2

Experiment 1 was repeated using 2 g of powdered sodium thiosulphate. Record the temperature in the table.

   Experiments 3, 4 and 5

Experiment 1 was repeated using 3 g, 4 g and 5 g of powdered sodium thiosulphate respectively. Record the temperatures in the table.

5-1-q2a

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2b1 mark

What type of chemical reaction occurs when sodium thiosulphate dissolves in water?

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2c2 marks

Explain how the temperature changes would differ in the experiments if 40 cm3 of water were used.

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2d2 marks

Suggest one change you could make to the apparatus used in the experiments to obtain more accurate results.

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3a1 mark

Ammonia is produced when aqueous sodium hydroxide is warmed with ammonium sulfate. Ammonia is less dense than air and very soluble in water. The apparatus below was used to prepare a sample of dry ammonia gas.

12-1-q4a

Name substance C.

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3b1 mark

Name substance D.

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3c1 mark

What necessary piece of equipment is missing in the diagram?

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3d1 mark

Suggest why concentrated sulfuric acid should not be used to dry ammonia.

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3e4 marks

There are two other mistakes in the apparatus shown in the diagram. Identify and explain these mistakes.

mistake 1 ..........................................................................................................................
explanation .......................................................................................................................
mistake 2 ..........................................................................................................................
explanation .......................................................................................................................

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1a1 mark

A student investigated the effect of temperature on the rate of reaction between sodium thiosulfate solution and dilute hydrochloric acid:

Na2S2O3 (aq) + 2HCl (aq)  → 2NaCl (aq) + S (s) + SO2 (g) + H2O (l)

The reaction between these two substances produces a precipitate which makes the mixture turn cloudy. 

A student timed how long it took until the cross could no longer be seen through the precipitate, shown in Figure 1.

They then calculated the rate of reaction and repeated the experiment at different temperatures. 

Figure 1 

c3oYktGM_disappearing-cross-experiment

Name the product that made the mixture go cloudy.

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1b2 marks

Suggest two control variables for the investigation that would ensure valid results are obtained.

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1c3 marks

Define the terms:

i)
Solution 
[1]
ii)
Solvent
[1]
iii)
Solute 
[1]

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1d2 marks

From the products formed in part a) identify:

i)
The solute
[1]
ii)
The solvent 
[1]

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2a2 marks

Rock salt is a mixture of sand and salt. Salt dissolves in water while sand does not. 

A group of students separated rock salt. 

They used the following method.

  1. Add the rock salt to a beaker.

  2. Add 250 cm3 of water.

  3. Leave without disturbing to allow the sand to settle to the bottom.

  4. After a while, filter the salt water into an evaporating dish.

  5. Heat the evaporating dish with a Bunsen burner until salt crystals begin to form.

i)
Suggest one improvement to step 2 that the students could have done to make sure all the salt is dissolved.
 
[1]
 
ii)
What name is given to the solution when no more salt can dissolve at this specific temperature?
 
[1]

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2b2 marks

Identify the residue and filtrate in step 4. 

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2c1 mark

Suggest one safety precaution the students should take in step 5.

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2d2 marks

Another student separated water from salty water using the apparatus in the diagram below.

 

saltwater-distillation-aqa-sq-1-1m-7d
 

By referring to points 1 and 2 in the diagram, describe how this technique works.

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2e1 mark

Identify the residue in the experiment being carried out in part (d).

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