Past Paper_detection And Analysis

Chemistry HKCEE Past Paper Detection and AnalysisP1/7

Section 9: Detection and Analysis and Other topics 1. In each of the following groups of substances, there is ONE substance which is different from the others in terms of their properties. In each group, identify the substance which is different from the others and explain your choice. (a) argon, fluorine, helium, neon (b) nylon, perspex, polyethene, urea-methanal (c) milk of magnesia, soap, vinegar, window cleaner

(d) carbon monoxide, hydrogen, methane, nitrogen

(8 marks) [1995-CE-2]

2. A student suggested the following immediate actions to deal with three domestic accidents. However, these actions are considered inappropriate. Accident 1. Some drain cleaner, which contains mainly concentrated sodium hydroxide solution, is split

Suggested action Use vinegar to neutralize the sodium hydroxide solution left on the hand.

onto the hand. 2. During cooking, some oil in a cooking pan

Use water to put out the fire.

catches fire. 3. Leakage of town gas occurs in a kitchen.

Turn on an exhaust fan in the kitchen to remove the town gas.

In each case, explain why the action is inappropriate and suggest a proper action.

[8 marks] [1996-CE-1]

3. For each of the following experiments, state the expected observation and write a relevant chemical equation. (a) Ethene is passed into an acidified potassium permanganate solution. (b) A mixture of butane and bromine vapour is exposed to diffused sunlight.

(c) A sodium sulphite solution is added to an iodine solution (iodine dissolved in aqueous potassium iodide).

(6 marks) [1998-CE-2]

4. For each of the following experiments, state ONE observable change and write a chemical equation for the reaction involved. (a) Dilute nitric acid is added to magnesium powder in a beaker. (b) A small piece of calcium is placed in a Bunsen flame.

(c) A mixture of copper(II) oxide and carbon powder is heated in a test tube.

(6 marks) [1999-CE-2]

Chemistry HKCEE Past Paper Detection and AnalysisP2/7

5. The diagram below shows a bottle of chemical waste in a school laboratory.

Describe and explain how you would remove kerosene and iron(III) ions from the chemical waste. (You may use any apparatus and chemicals available in a school laboratory.)

(8 marks) [1999-CE-5]

6. Manufacturing ammonia by the Haber process involves the following exothermic reaction: N2 (g) + 3 H2 (g) (i)

2 NH3 (g)

(1) Name a catalyst used in the process. (2) Suggest how the heat liberated in the reaction can be used in the process.

(ii)

A sufficient amount of hydrogen and 6.0 x 103 dm3 of nitrogen, measured at room temperature and pressure, are allowed to react in the reaction chamber to give ammonia. Suppose that the conversion of nitrogen to ammonia is 15%. Calculate the mass of ammonia formed.

(iii)

Upon reaction with a suitable chemical, ammonia gives a nitrogenous fertilizer. Write a chemical equation for such a reaction.

(iv)

Most window cleaners contain ammonia solution as an active ingredient. (1) Explain why ammonia solution is used in window cleaners. (2) State ONE reason for using ammonia solution instead of sodium hydroxide solution in window cleaners.

(Molar volume of gas at room temperature and pressure = 24.0 dm3) (9marks) [1999-CE-8b] 7. Six compounds are classified into two groups as shown in the table below: Gas

Solid

Ammonia

Iron(III) oxide

Carbon dioxide

Magnesium oxide

Nitrogen dioxide

Potassium oxide

Reclassify these compounds into two groups according to (a)

one of their physical properties, and

(b)

one of their chemical properties.

(4 marks) [2000-CE-1]

Chemistry HKCEE Past Paper Detection and AnalysisP3/7

8. Explain the following statements: i.

In cold weather, a person trying to warm up a room with a coal fire soon gets dizzy.

ii.

Detergents can be used to clean up oil spillage in the sea.

(5

marks) [2000-CE-6c] 9. State whether each of the following statements is true or false. Explain your answer in each case. i.

The melting point of sodium chloride is much higher than that of methane because the ionic bonding in sodium chloride is much stronger than the covalent bonding in methane.

ii.

When concentrated sulphuric acid is diluted, water should be added slowly to the acid.

(4

marks) [2000-CE-8c] 10. A small piece of sodium is added to a tall jar containing two layers of liquids, paraffin oil and water with a few drops of phenolphthalein, as shown in the diagram below. Describe and explain all expected observations. (Density of sodium = 0.97 g cm-3, density of paraffin oil used = 0.82 g cm-3)

(9 marks)

[2001-CE-4] 11. The flow diagram below shows the four key stages in the production of ammonium nitrate from ammonia. Ammonia

Stage I

Compound X

Stage II

Nitrogen dioxide

Stage III Ammonium i.

Stage IV

Nitric acid

(1) Give the name of X. (2) Write a chemical equation for the reaction in Stage I.

ii.

Is the reaction in Stage II a redox reaction? Explain your answer in terms of oxidation number.

iii.

Suggest how nitrogen dioxide can be converted to nitric acid in Stage III.

Chemistry HKCEE Past Paper Detection and AnalysisP4/7

iv.

Suggest ONE use of ammonium nitrate in daily life.

v.

Ammonium nitrate can be prepared by reacting ammonia with nitric acid. Calculate the theoretical volume of ammonia gas, measured at room temperature and pressure, required to produce 5.0 g of solid ammonium nitrate.

(Molar volume of gas at room temperature and pressure = 24 dm3)

(9 marks) [2001-CE-8b]

12. For each of the following experiments, state an expected observation and write a chemical equation for the reaction involved. (a)

A magnesium ribbon is placed in a Bunsen flame.

(b)

Excess iron(II) sulphate solution is added to an acidified potassium permanganate solution.

(c)

Chlorine gas is bubbled into a sodium bromide solution.

(6 marks) [2002-CE-2]

13. Consider the substances listed below: ammonia, manganese(IV) oxide, potassium hydroxide, sodium benzoate, sodium dichromate, sodium nitrite (a)

Which substance is used to preserve bacon? State how it works.

(b)

Which substance is used in zinc-carbon cells? State its function.

(c)

Which substance is used in breathalysers to detect the presence of ethanol in the breath of suspected drunk drivers? State the expected observation in the breathalyser if a positive result is obtained.

(6

marks) [2002-CE-3]

14. Ammonia was once used to detect the leakage of chlorine in chemical plants. If there was a leakage, white fumes would be observed. The word equation below represents the reaction of chlorine with ammonia: chlorine + ammonia --> ammonium chloride + nitrogen (i)

Transcribe the word equation into a chemical equation.

(ii)

Suggest what the white fumes might have been.

(3 marks) [2002-CE-7c]

15. Ammonia gas can be prepared by heating a mixture of ammonium chloride and calcium oxide in the set-up shown below:

Chemistry HKCEE Past Paper Detection and AnalysisP5/7

i.

The reaction of ammonium chloride with calcium oxide also gives calcium chloride as a product. Write the chemical equation for the reaction of ammonium chloride with calcium oxide.

ii.

Why is it necessary to clamp the test tube with its mouth pointing downwards as shown?

iii.

Decide which of the following set-ups, (I), (II) or (III), should be connected to the delivery tube to collect the ammonia gas produced. Explain your answer.

iv.

Calculate the theoretical volume of ammonia gas, measured at room temperature and pressure, which can be obtained from the reaction of 1.0 g of ammonium chloride with excess calcium oxide. (Molar volume of gas at room temperature and pressure = 24 dm3)

(7 marks) [2003-CE-6a]

16. Ammonia is manufactured by the Haber process. In the process, a mixture of nitrogen and hydrogen is passed over heated iron in the reaction chamber. The reaction of nitrogen with hydrogen can be represented by the following equation: N2 (g) + 3H2 (g)

2NH3 (g)

i.

What does the sign ‘

ii.

What is the function of iron in the reaction chamber?

iii.

As air contains about 78% of nitrogen by volume, can air be used instead of nitrogen in the

’in the equation stand for?

reaction chamber? Explain.

iv.

In the process, only about 15% of the nitrogen is converted to ammonia. Suggest how the gaseous mixture that emerges from the reaction chamber can be treated so as to reduce the wastage of raw materials.

(6 marks) [2003-CE-6b]

17. Explain why filtration can be used to remove mud particles from muddy water, but cannot be used to remove sodium chloride from sea water.

(3 marks) [2003-CE-7c]

Chemistry HKCEE Past Paper Detection and AnalysisP6/7

18. For each of the following pairs of substances, suggest a chemical test to distinguish one substance from the other and state the expected observations. (a)

table salt and white sugar

(b)

ammonium chloride and potassium chloride

(c)

dilute sulphuric acid and dilute nitric acid

(6 marks) [2004-CE-2]

19. Draw a labelled diagram to show the experimental set-up that can be used in the separation of water from an aqueous solution of sodium chloride.

(3 marks) [2005-CE-S-4]

20. Aspirin is a painkiller. It has the following structure: O O C CH3 CO2H

(i) (1) Intake of aspirin may lead to certain adverse side effects. State ONE such adverse side effect. (2) Give ONE other commonly used painkiller, which does not have the side effect that you have stated in (l). (ii) Aspirin can be converted to salicylic acid in two steps as shown below:

O O C CH3

OH

CO2H

Step 1

NaOH (aq) + heat aspirin

a sodium salt of salicylic acid

CO2H

Step 2

salicylic acid

(1) Suggest a structure for the sodium salt of salicylic acid formed in Step 1. (2) Suggest a reagent that can be used in Step 2. (3)

In an experiment to convert aspirin acid, 5.6 g of salicylic acid was obtained from 9.0 g of aspirin. Calculate the percentage of aspirin that had been converted to salicylic acid.

Chemistry HKCEE Past Paper Detection and AnalysisP7/7

(Molar mass of aspirin = 180.0 g; molar mass of salicylic acid = 138.0g)

(7 marks) [2004-CE-9c]

21. There are four unlabelled reagent bottles each containing one of the white solids listed below ammonium chloride, ammonium nitrate, sodium hypochlorite and sodium sulphate Suggest how you would carry out tests to distinguish the four solids from one another.

(9 marks) [2005-CE-12]