NNS chemistry past paper section 15

Topics: Sodium hydroxide, Sodium chloride, Chlorine Pages: 34 (4213 words) Published: September 24, 2013
NSS Chemistry Part 15 Analytical Chemistry (Structural Questions) HKCEE and HKAL Past Paper Questions
1. HKCEE 1994 Q8b
A student carried out some tests on an ionic compound X which was a white solid. The results obtained were summarized in the following flow diagram:


Based on the above information, deduce the cation and anion present in X.


Describe how the flame test on X can be carried out in the laboratory. (6 marks)


2. HKCEE 1995 Q2
In each of the following groups of substances, there is ONE substance which is different from the other in terms of their properties. In each group, identify the substance which is different from the others and explain your choice.


argon, fluorine, helium, neon


nylon, perspex, polyethene, urea-methanal


milk of magnesia, soap, vinegar, window cleaner


carbon monoxide, hydrogen, methane, nitrogen
(8 marks)


3. HKCEE 1996 Q6b
A, B, C and D are four unlabelled bottles, each containing one of the following reagents: 2M ammonia solution, 2M ethanoic acid,
2M hydrochloric acid, 2M nitric acid
The following scheme is used to identify the four reagents:


? Explain
What is the reagent in bottle A? Explain why this reagent turns red litmus paper blue.


What is the reagent in bottle B? Write a chemical equation for the reaction between this reagent and copper ?
turnings, and a chemical equation for the formation of the brown fumes.



Suggest a test to distinguish between the reagent in bottles C and D. (Smelling the reagents in NOT an acceptable answer.)


State the observable change in this test and explain your answer. (8 marks)



4. HKCEE 1998 Q5
Each of five unlabelled bottles contains one of the following chemicals: 2 M hydrochloric acid

2 M nitric acid

2 M sodium chloride solution

2 M sodium hydroxide solution

distilled water
Suggest how you would carry out tests to identify the contents of each bottles, using the materials and apparatus listed below. Your answer should include the observation of each test. Copper foil, solid copper(II) carbonate, 2 M copper(II) chloride solution, test tubes and a Bunsen burner

(You are Not required to write chemical equations. Answer in the form of flow diagrams will NOT be marked.)
(8 marks)


5. HKCEE 1999
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)


6. HKCEE 2003 Q7c
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)

Sea water is a solution while muddy water is a suspension. The size of ions in sea water is much smaller than that of the mud particles in muddy water.
Ions in sea water can pass through pores in filter device while particles cannot.

7. HKCEE 2004 Q2
For each of the following pairs of substances, suggest a chemical test to distinguish one substance from the other and state the expected observations.

table salt and white sugar


ammonium chloride and potassium chloride


dilute sulphuric acid and dilute nitric acid
(6 marks)


Treat the substances with conc. H2SO4.
White sugar turns black, while slat gives misty fumes.


Warm the substances with NaOH.
NH4Cl(s) reacts with NaOH(aq) to give an alkaline gas, while KCl(s) does not.


Heat the acids with copper metal.
Only HNO3(aq) gives gas bubbles.


8. HKCEE 2004 Q8c
A policeman suspected a car driver to have drunk an excessive amount of alcoholic drinks, and used a dichromate breathalyser to conduct a test on the driver’s breath. The result was positive. (i)

State the principle underlying the test of ethanol using a dichromate breathalyser.


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