POK OI HOSPITAL TANG PUI KING MEMORIAL COLLEGE

SECOND TERM EXAMINATION ( 1997-1998 )

S4 CHEMISTRY I

Class : ________________ Date : __________________

Name : ________________ Time allowed: 90 minutes

Class Number : ________________ ( P.1 - P.5 /53 )

Instructions to students:

1.Ther are TWO sections in this paper, Section A and Section B.

2.Answer ALL questions.

3. Write your answers on the foolscap papers provided.

4. The total score is 90 marks.

________________________________________________________________________

Section A : Answer ALL questions ( 36 % )

X, Y and Z are three elements with atomic numbers between 5 and 20. The following table provides some information about these elements.

	Element X	Element Y	Element Z
Number of electrons in the outermost shell of the atom	1	4	6
Appearance at room temperature and pressure	Grey solid	Black solid	Yellow solid

(a) Which of the elements is metal?

(b) Name elements Y and Z.

(1) Draw electron diagrams for P and Q, showing the outermost shell electrons only.

(2) Explain whether Pm or Q has a higher melting point.

(6 marks)

Rubidium (Rb) and potassium belong to the same group in the periodic table. The relative atomic mass of rubidium is higher than that of potassium.

(a) Explain whether rubidium is more reactive than potassium.

(b) Write a chemical equation for the reaction between rubidium and water.

(State symbols should be given.)

(d) Suggest ONE safety precaution for handling rubidium in the laboratory.

(5 marks)

In the following diagram, the half cell X contain iron(II) sulphate solution and the half cell Y contains acidified potassium dichromate solution. The beakers are connected by a salt bridge.

The following reactions take place in the two half-cells.

Half cell X: Fe²⁺ (aq) ® Fe³⁺ (aq) + e^-

Half cell Y: Cr₂O₇(aq) + H⁺ (aq) + e^- ® Cr³⁺ (aq) + H₂O (l)

(a) Suggest suitable material for electrodes A and B.

(b) Balance the half-equation of half cell Y.

(d) Explain briefly, in terms of oxidation number, why reduction takes place in half cell Y.

(e) In what direction would the elements flow in the circuit?

(5 marks)

(a) Arrange the following substances in the order of increasing pH and explain your answer.

1 M ethanoic acid, 1 M hydrochloric acid, 1 M sulphuric acid

(b) Three solution samples, A, B, C, are being tested for the purpose of perming hair. The table below lists the pH of these samples:

Sample	PH
A	6.5
B	8.5
C	10.0

What sample is most suitable for perming hair? Explain your answer.

( 5 marks)

Describe how you can prepare large crystals of potassium sulphate in the school laboratory.

( 8 marks)

(Your are required to give paragraph-length answer to this question. 3 of the marks will be awarded for the effective communication of knowledge in Chemistry.)

Three bottles of dilute acids are labeled as X, Y and Z. One of them contains dilute nitric acid, another dilute sulphuric acid and the remaining one dilute hydrochloric acid. The table below summarizes the results of adding calcium to the three acids:

Observation

Test

Adding calcium to the acid

A brown gas appears near the mouth

A colourless gas is rapidly evolved but the reaction soon slows down and then stops.

A colourless gas is rapidly evolved.

(a) Identify X and Y.

In each case, explain how the observations lead to your identification.

(b) Write chemical equations for the reaction between

(1) calcium and dilute hydrochloric acid;

(2) calcium and dilute nitric acid.

( 6 marks)

Section B : Answer ALL question. ( 54 marks)

(a) A student carried out a copper-plating experiment in the laboratory using the set-up shown below:

(1) Which electrode is the cathode?

(2) Which electrode is the anode?

(3) Explain why copper(II) sulphate solution can conduct electricity.

(4) What would be observed at the carbon rob during the experiment?

Write a half equation for the reaction involved.

(5) In the copper-plating industry, a metalis used instead of the carbon rob.

What is this metal? Write a half equation for the reaction involved.

(6) Write a half equation for the reaction at the key.

(7) Suggest ONE reason why it is necessary to remove the copper(II) ions from the waste water before discharging from the copper-plating factory.

( 9 marks)

(b) (1) Consider the following hazard warning labels:

Choose TWO labels which should be displayed on a bottle of concentrated nitric acid. Explain your choice.

(2) What would be observed when concentrated nitric acid is added dropwise to

(i) a solution of iron(II) compound?

(ii) zinc granules?

Explain the observations and write appropriate equations.

( 9 marks)

(a) A domestic drain cleaner contains concentrated sulphuric acid as the active ingredient. A student carried out the following experiment to find out the concentration of sulphuric acid in the drain cleaner.

1.0 cm³of the drain cleaner was diluted to 500 cm³ with distilled water.25.0cm³ of the diluted drain cleaner solution were measured and transferred to a conical flask. The solution in the flask required 18.2cm³ of 0.10 M sodium hydroxide solution for complete neutralization.

(1) Name the apparatus used to measure 25.0cm³ of the diluted solution.

(2) Write a chemical equation for the reaction between sulphuric acid and sodium hydroxide solution.

(3) Calculate (i) the number of moles of sodium hydroxide in 18.2cm³ solution.

(ii) the number of moles of sulphuric acid in 25.0cm³ solution

(iii) the number of moles of sulphuric acid in 500 cm³ solution.

(iv) The molarity of sulphuric acid in 1.0cm³ drain cleaner solution.

(4) Suggest ONE disadvantage of using concentrated sulphuric acid for cleaning iron pipes.

(5) State ONE safety precaution needed when using concentrated sulphuric acid.

Explain your answer.

( 11 marks)

(b) (1) How many molecules are there in 0.5 mole of carbon dioxide molecules?

(2) How many atoms are present in 0.5 mole of carbon dioxide molecule?

(3) What is the molar mass of calcium chloride (CaCl₂)?

(4) Calculate the number of moles of calcium chloride present in 3.33g of it.

(Relative atomic masses: Ca=40.0, Cl=35.5.

The Avogadro constant=6.02 ´ 10²³ mol )

( 7 marks)

(a) The following chart shows the reaction between substance A and dilute hydrochloric acid:

(1) Name the substances A and B.

(2) Give a balanced chemical equation for the reaction between substance A and dilute hydrochloric acid.

(3) What happens if concentrated hydrochloric acid is used instead of dilute hydrochloric acid when reacting with substance A?

(4) Suggest one test for the carbon dioxide gas.

( 6 marks)

(b) Antacid tablets (containing calcium carbonate as the active ingredient) are used to relieve pains caused by excess acid in the stomach. The following experiment was performed by a student to find out the amount of calcium carbonate in an antacid tablet.

He weighed a tablet (mass=1.2g) and then dissolved the tablet in distilled water to form a solution. It was found that the solution required 15.2cm³ of 1.00 M hydrochloric acid for complete neutralization.

(1) In this experiment, standard hydrochloric acid is used. What is the meaning of the term ‘standard’?

(2) Explain why effervescence was observed when adding hydrochloric acid to the solution containing the antacid tablet.

(3) Calculate the percentage by mass of calcium carbonate in one antacid tablet.

(Relative atomic masses: C=12.0, O=16.0, Ca=40.0)

(4) Antacid tablets containing calcium carbonate are seldom used nowadays. Instead, magnesium hydroxide is usually used as the active ingredient.

(i) Suggest one reason why magnesium hydroxide is preferred to calcium carbonate.

(ii) Write a chemical equation for the reaction involved.

( 12 marks)

END OF PAPER

POK OI HOSPITAL TANG PUI KING MEMORIAL COLLEGE

SECOND TERM EXAMINATION ( 1997-1998 )

S4 CHEMISTRY II

Class : ________________ Date : __________________

Name : ________________ Time allowed: 1 hour

Class Number : ________________ ( P.1 - P.9 /53 )

Instructions to students:

1. Answer ALL questions.

2. Note that you may only mark ONE answer to each question. Two or more answers will score NO MARKS.

3. All questions carry equal marks. No marks will be deducted for wrong answers.

4. Write your answers on the multiple choice answer sheet provided.

5. The total score is 50 marks.

________________________________________________________________________

There are 50 questions in this paper.

Which of the following describes the atomic structure of an atom with a mass number of 40?

Number of protons Number of neutrons Number of electrons

A. 18 22 22

B. 18 18 22

C. 20 18 20

D. 20 20 20

The electron diagram of a compound formed between an element X and oxygen is shown below:

Which of the following would be the most likely chemical formula for the nitrate of X?

A. X₂NO₃ B. X(NO₃)₂ C. X(NO₃)₃ D. X₂(NO₃)₃

Which of the following substances has a simple molecular structure?

A. Diamond B. Copper C. Nitrogen D. Quartz

Boron consists of two isotopes. The table below lists the relative abundance of these two isotopes.

Isotope	Relative abundance
B	19.7%
B	80.3%

The relative atomic mass of boron (correct to 1 decimal place) is

A. 10.4 B. 10.6 C. 10.8 D.11.0

Which of the following electron diagrams is correct?

(Only the outermost shell electrons are shown.)

Which of the following metals is most suitable for making hot water pipes?

A. Copper B. Iron C. Lead D. Sodium

No reaction takes place in one of the following processes. Which process is it?

A. Calcium and cold water B. Platinum and dilute hydrochloric acid

C. Iron and steam D. Zinc and dilute sulphuric acid

Which of the following chemical equation is NOT balanced?

A. 4Al (s) + 3O₂ (g) ® 2Al₂O₃ (s)

B. 3Fe (s) + 2O₂ (g) ® Fe₃O₄ (s)

C. Zn (s) + 2HCl (aq) ® ZnCl₂ (aq) + H₂ (g)

D. K (s) + 2H₂O (l)® KOH (aq) + H₂ (g)

Which of the following is NOT a typical property of metals?

A. Good conductor of heat B. Malleable

C. Soluble in water D. Ductile

The chemical properties of an element depend on

A. its relative atomic mass.

B. the number of isotopes of the element.

C. the number of electron shells in its atoms.

D. the number of outermost shell electrons in its atom

Which of the following experiments can be used to show that concentrated sulphuric acid is a dehydrating agent?

A. Adding it to copper(II) oxide powder

B. Adding copper(II) sulphate crystals

C. Adding it to calcium carbonate powder

D. Adding it to sodium chloride crystals

In which of the following cases will the iron nail rust most SLOWLY?

Consider the following simple chemical cell.

Which of the following statements concerning the chemical cell is CORRECT?

A. The copper strip is the negative electrode.

B. The magnesium strip increases in mass

C. The concentration of magnesium ions in the electrolyte remains the same.

D. Chemical energy is changed into electrical energy.

In which of the following compounds does nitrogen have the LOWEST oxidation number?

A. NH₃ B. NO C. NO₂ D. HNO₃

Which of the following methods can produce hydrogen?

(1) Adding zinc to water

(2) Electrolyzing dilute sulphuric acid

(3) Adding magnesium to dilute hydrochloric acid

A. (1) and (2) only B. (1) and (3) only

C. (2) and (3) only D. (1), (2) and (3)

Direction: Questions 16-17 refer to the following chemical cell. A brown colour

appears around the electrode of the left beaker.

Which of the following ions are oxidized?

A. Iodide ions B. Iron(III) ions

C. Potassium ions D.Sulphate ions

Which of the following statements is/are CORRECT?

(1) The potassium iodide solution changes from brown to colourless.

(2) The iron(III) sulphate solution changes from yellow to green.

(3) Electrons flow from the potassium iodide solution to iron(III) sulphate solution to external circuit.

A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only

Consider the following chemical equation:

2HNO₃ (aq) + CaCO₃ (x) ® Ca(NO₃)₂ (y) + H₂O (z) + CO₂ (g)

Which of the following combination is CORRECT?

x y z

A. aq aq l

B. aq aq aq

C. s aq l

D. s s aq

An acid is best described as

A. a compound containing hydrogen atoms.

B. a compound which reacts with an alkali.

C. a hydrogen-containing substance that gives hydrogen ions when dissolved in water.

D. a hydrogen-containing substance that gives hydrogen ions as the only positive ion when dissolved in water.

Which of the following household materials contain an acid?

A. milk of magnesia B. window cleaner C. soap D. vinegar

What gas is liberated when magnesium reacts with lemon juice?

A. carbon dioxide B. sulphur dioxide C. oxygen D. hydrogen

Which of the following CANNOT change the colour of a piece of dry pH paper?

A. dilute nitric acid B. dilute hydrochloric acid

C. dilute sulphuric acid D. solid critic acid

When a fizzy drink tablet is added to a cup of water, effervescence occurs. This is due to formation of

A. carbon dioxide B. hydrogen

C. oxygen D. a mixture of hydrogen and oxygen

Concentrated nitric acid is corrosive because of its

A. acidic property. B. oxidizing property

C. reducing property D. dehydrating property

Which of the following about concentrated sulphuric acid is INCORRECT?

A. It is a powerful oxidizing agent.

B. When it reacts with copper, hydrogen gas is given off.

C. It can acts as a dehydrating agent.

D. Its corrosive nature is due to the dehydrating and oxidizing properties.

The change in oxidation number in nitrogen in concentrated nitric acid when it reacts with copper is

A. from +4 to +5 B. from +5 to +4

C. from +6 to +5 D. from +4 to +6

Which of the following would occur if a few drop of water is added to a beaker of concentrated sulphuric acid?

(1) A great amount of heat is liberated.

(2) Water will change into steam.

(3) Concentrated sulphuric acid will spurt out.

A. (1) and (2) only B. (1) and (3) only

C. (2) and (3) only D. (1), (2) and (3)

Sulphuric acid is NOT used to prepare carbon dioxide from limestone because

A. there is no reaction between sulphuric acid and limestone.

B. The reaction between sulphuric acid and limestone is too vigorous.

C. Sulphuric acid is a strong oxidizing agent.

D. An insoluble product is formed which stops further reaction.

Which of the following processes should NOT be attempted in the laboratory?

A. Adding a small piece of calcium to water.

B. Evaporating a copper(II) sulphate solution.

C. Heating ammonium sulphate with calcium hydroxide.

D. Adding water to concentrated sulphuric acid.

Which of the following is NOT a suitable method of preparation?

A. Preparation of carbon dioxide from calcium carbonate and dilute sulphuric acid

B. Preparation of hydrogen from iron and dilute sulphuric acid.

C. Preparation of sulphur dioxide from sodium sulphite and dilute hydrochloric acid

D. Preparation of nitrogen dioxide from zinc and concentrated nitric acid.

Which of the following solutions will NOT give a precipitate with dilute sodium hydrogen solution?

A. CuSO₄ (aq) B. FeSO₄ (aq) C. KCl (aq) D. ZN(NO₃)₂ (aq)

Metal X reacts with dilute nitric acid to give a colourless solution. When sodium hydroxide solution is added to the solution, a white precipitate which dissolves in excess sodium hydroxide solution is formed. X is probably.

A. copper. B. iron. C. lead. D. magnesium.

How many moles of atoms are there in 60.0g of calcium?

A. 1.00 moles B. 1.50 moles C. 2.00 moles D. 2.50 moles

The molecular formula of a gaseous element X is X_2. If the relative atomic mass of X is 19, what is the number of molecules in 114g of the gas?

(Avogadro constant = 6.02´10²³ mol^-1)

A. 3 B. 6

C. 3 ´ 6.02 ´ 10²³ D. 6 ´ 6.02 ´ 10²³

Which of the following contains the same number of atoms as 2.2g of carbon dioxide?

(Relative atomic masses: H=1.0, C=12.0, N=14.0, O=16.0, S=32.0, Cl=35.5)

A. 1.70g of ammonia B. 2.25g of nitrogen monoxide

C. 2.80g of sulphur dioxide D. 3.55g of chlorine

What is the number of mole of ions present in 50.0g of iron(III) sulphate[Fe₂(SO₄)₃]?

(Relative atomic masses: Fe= 56.0, O=16.0, S=32.0)

A. 0.125 mole B. 0.250 mole C. 0.5.. mole D. 0.625 mole

A 2.0 M sodium chloride solution is prepared by dissolving 11.7g of sodium chloride in distilled water. What is the volume of the solution formed?

(Relative atomic masses: Na=23.0, Cl=35.5)

A. 50.0cm³ B. 100.0 cm³ C. 250 cm³ D. 500.0 cm³

How much water must be added to 100 cm³of 0.50 M NaCl solution to make it 0.01M?

A. 300 cm³ B. 400 cm³ C. 500 cm³ D. 600 cm³

Which of the following solutions has the highest pH value?

A. 1 M ammonia solution B. 1 M potassium hydroxide solution

C. 1 M sulphuric acid D. 1 M sodium sulphate solution

The molarity of an aqueous solution of potassium hydroxide, KOH (formula mass= 56)containing 11.2g of KOH in 500 cm³ solution is

A. 0.2 M B. 0.3 M C. 0.4 M D. 0.5 M

What mass of sulphuric acid (H₂SO₄) is present in 200 cm³ of 2 M sulphuric acid? (Relative atomic masses: H=1.0, S=32.0, O=16.0)

A. 19.6g B. 39.2g C. 58.8g D. 80.0g

What volume of 0.250 M hydrochloric acid is required to react completely with 25.0 cm³ of 0.150 M sodium carbonate solution?

A. 15.0 cm³ B. 25.0 cm³ C. 30.0 cm³ D. 40.0 cm³

Which of the following substances will react with dilute hydrochloric acid to form salt and water only?

(1) CaCO₃ (2) CuO (3) Mg(OH)₂

A. (1) and (2) only B. (1) and (3) only

C. (2) and (3) only D. (1), (2) and (3)

Which of the following substances would react with sodium hydroxide solution?

(1) Ammonium chloride solution

(2) Copper(II) sulphate solution

(3) Ethanoic acid

A. (1) and (2) only B. (1) and (3) only

C. (2) and (3) only D. (1), (2) and (3)

Directions: Each question below (Question Nos, : 45 to 50)consists of two separate statements. Decide whether each of the two statements is true of false. If both are true, then decide whether ot not the second statement is a correct explanation of the first statement. The select one option from A to D according to the following table:

A. Both statements are true and the 2nd statement is a correct explanation of the 1st statement.

B. Both statements are true but the 2nd statement in NOT a correct explanation of the 1st statement.

C. Only one statement is true while the other is false.

D. Both statements are false.

1st statement 2nd statement

45. Argon and neon are chemically reactive	Atoms of argon and neon have 8 outermost shell electrons.
46. Magnesium reacts with dilute sulphuric acid to give hydrogen.	All metals react with dilute acids.
47. Chlorine is discharged at the anode during the electrolysis of concentrated sodium chloride solution using carbon electrodes.	The concentration of chloride ions in the solution is much higher than that of hydroxide ions.
48. Concentrated hydrochloric acid can react with silver.	Concentrated hydrochloric acid is a strong oxidizing agent.
49. If a student accidentally spills some hydrochloric acid on his hand, he should immediately wash his hand with sodium hydroxide solution.	Sodium hydroxide solution can neutralize hydrochloric acid.
50. Both zinc and molten sodium chloride sodium chloride conduct electricity.	Both zinc and molten sodium chloride contain mobile ions.