Common Mistakes for Paper 2 and 3

7/31/2019 Common Mistakes for Paper 2 and 3

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PROGRAM KECEMERLANGAN KIMIA SMKTTA

TEKNIK MENJAWAB SOALAN KERTAS 2& 3 KIMIA

Disediakan Oleh: Rudi Bin ZainalCommon mistakes for paper 2 and 3

The question normally starts with a command word. Students must know the meaning of

the command word to make sure that the answer given is according to the questionsrequirement.Match the command word to the mark allocated for each question.

What is meant by..(Definition)

- Give the exact meaning

1. Define the meaning of nucleon number?Wrong answer: sum of proton number and neutron numberCorrect answer:

2. Define the meaning of melting point?Wrong answer: Melting point is the point where solid starts changes to liquid.Correct answer:

3. Define the meaning of empirical formulaWrong answer: show the simplest ratioCorrect answer:

4. Define the meaning of molecular formula

Wrong answer: real number/actual number of atomCorrect answer:

5. Define the meaning of hydrocarbon?Wrong answer: Compound that consist of carbon and hydrogenCorrect answer:

6. What is the meaning of number of proton and number of nucleon referring to atomsodium?[number of proton sodium = 11,Number of neutron sodium = 12]

7. Explain the meaning ofisotope with example that suitable.Wrong answer: same number of proton but different number of nucleonCorrect answer:

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8. Define the meaning of acid?Wrong answer: Substances that containing of hydrogen ionCorrect answer:

9. Define alloy?Wrong answer: mix of 2 metalCorrect answer:

10. Define the meaning of rate of reaction?Wrong answer: changes of reactant or product with time.Correct answer:

Name/State the name

-Give the name , not the formula.

11. State the name of catalyst used in contact process?Wrong answer: V2O5, vanadium oxideCorrect answer:

12. Name the main element added to copper to form bronze.Wrong answer : Sn.Correct answer :

Simple Experiment /Chemical test

Tips : All the experiment/ chemical test must haveprocedure andresult.

13. How to verify a gas that released in electrolysis and it is a chorine gas?Wrong answer: test using blue litmus paper and it will change to red colour.

Correct answer:

14. How to verify hydrogen gas?Wrong answer: test using burning wooden splinterCorrect answer:

15. How to verify oxygen gas?wrong answer: test using glowing wooden splinter

Correct answer:

16. How to verified presence of iron(III) ion in aqueous?Wrong answer: add sodium hdroxide ecessively, coclate colour percipitate formedCorrect answer:

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Another example common mistakes that candidate do.

24. Write the electron arrangement of Sodium?Wrong answer: 2:8:1

Correct answer25. Draw the diagrammatic diagram of magnesium atom?(Proton number: 12)Wrong answer:

26. What is the function of salt bridge?

Wrong answer: to complete the circuitCorrect answer:

27. Sketch graph of temperature against time for melting point of naphthalene. Why at themelting point a substance, temperature of substance did not increase although heating iscontinuously?

Wrong answer: because heat is absorbed is used to overcome attraction of particlesCorrect answer:

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Salt bridge


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28. Give 1 special characteristic for transition element with example.Wrong answer:1) as catalyst in chemical reaction

2) Can form color solutionCorrect answer:

29. State the one use of sulphuric acidWrong answer: as fertilizer

As battery carCorrect answer:

30. Explain this ionic equationCu Cu 2+

Wrong answer: copper releases 2 electrons to become copper ionCorrect answer:

CHEM-DRAW31. Tick () or (x) in box that provided for the correct diagram of stop cork.

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What is the mistakes student have done?

PAPER 2 STRUCTURE

1 In an experiment to determine the empirical formula of an oxide of copper, thecombustion tube with the porcelain dish is weighed. Oxide of copper is added intothe porcelain dish and the tube is weighed again. The oxide of copper is heatedstrongly. After the set of apparatus cools down to room temperature the combustiontube with its content is weighed again.

The following data is obtained.

Mass of combustion tube + porcelain dish = 19.60 gMass of combustion tube + porcelain dish + oxide of copper= 25.68 gMass of combustion tube +porcelain dish + copper = 24.46 g

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Glass wool

+ C2H5OH

Burette

Basin thatcontaining water

Chips ofporcelain


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(a) What is meant by empirical formula?[ 1mark]

(b) Draw a labelled diagram of the set up of the apparatus for the experiment.

[ 2marks ]

(c) Calculate the empirical formula of the oxide of copper.Given that the relative atomic mass of O=16 , Cu=64

3 marks(d) Write the chemical equation for the reaction in the experiment.

[1 mark]

(e) Before oxide of copper is heated, hydrogen gas is allowed to pass throughthe apparatus until all the air in the combustion tube is completely removed.Describe the steps that should be taken to ensure that all air in thecombustion tube has been removed.

[3marks]

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(f) Can the empirical formula of aluminium oxide be determined using thesame method as above? Explain your answer.

[2 marks]

2 The figure shows part of the Periodic Table of Elements.V,W,X,Y and Z do notrepresent the actual symbol of the elements.1

182 13 14 15 16 17

V X Z

Y

W

(a) Write the electron arrangement of Y ion.

.[1 mark]

b (i) Which of the element is not chemically reactive.

.[1 mark]

(ii) Explain your answer in (b) (i).

....................................................................................................................

....... [1 mark](c) V and W are located in the same group in the Periodic Table of Elements.

(i) Which of the element is more reactive?..............................................................................................................

......... [1 mark]

(ii) Explain your answer in (c)(i).

.................................

.........................

........ [3 marks]

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(d) V reacts with Y to form a compound.State one physical property of the compound formed.

.....[1 mark]

(e) X reacts with Y to form a compound.Draw the electron arrangement for the compound formed.

[2 marks]

SECTION C (ESSAY QUESTIONS)

1. a) Compare the physical states that exist in matter in terms of particle arrangement,forces of attraction between the particles and the kinetic energy content.

[9marks](ans) : Matter exists in 3 physical states ; i.e. Solid, liquid, gas

Solid :Particles are compact and .. arranged .

The attractive force is . and the particles can only and vibrate in .position.The kinetic energy is .

Liquid :

Particles are less compact and are arranged in orderly manner.The attractive force is ., The particles form that move freely.The kinetic energy is

Gas :

Particles are not arranged at all and are ..The attractive force is very ...The kinetic energy is very ..

b) A solid has a melting point of 75 0C.Describe an experiment conducted in a laboratory to determine the melting point of solidX. Your answer must show how the melting point of solid A can be obtained.

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[11marks](Ans) ;Materials :

Apparatus : boiling tube, thermometer .. , beaker . cm3

retort stand + clamp, . , Procedure :

1. of solid X is filled into a boiling tube.

2. The thermometer is put into the boiling tube and the water is .

3. The content of the boiling tube is .. from time to time.

4. When the temperature reaches .. 0C, the stop watch is ..

5. The heating temperature is recorded at an interval of .. secondsuntil .. 0C.

Results :

Time / sTemperature/0C

The heating graph of solid X is plotted:Temperature/0C

__________________________ time/s

The melting point of solid X is read from the flat section of the graph;

i.e.

2.The table shows the proton number of atoms P, Q and R.

Element Proton number

PQR

81217

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(a) Based on electron arrangement, explain the formation of chemical bondbetween

(i) element P and element P[5 marks]

(ii) element Q and element R [7 marks ](b) Gas P reacts with element Q to produce a white solid.

(i) Write a chemical equation for the reaction between gas P and element Q.(ii) State three physical properties of the white solid.

[4 marks]

(c) What is the position of element Q in the Periodic Table of the elements?Explain how do you obtain your answer.

[4 marks]

GUIDELINE FOR ANSWERING PAPER 3

Structure Question 1/2 Test The Mastery of 11 Scientific Skills

1. Observing2. Classifying3. Inferring4. Measuring (burette , stopwatch, thermometer, voltmeter)5. Predicting6. Communicating( e.g construct table and draw graph)7. Space-Time Relationship8. Interpreting Data9. Defining Operationally10. Controlling Variables11. Hypothesizing

Each answer is allocated mark as follows: 3 marks/2 marks/1 mark/0 Score : 11 X 3 = 33

Question 3 (essay) Test The Mastery of Planning Experiment .

Planning should include the following aspects :1. Aim of the experiment/Statement of the problem2. All the variables3. Statement of the hypothesis4. List of substances/material and apparatus should be separated5. Procedure of the experiment6. Tabulation of data Score : (5 X 3) + 2 = 17

The question normally starts with certain situation related to daily life.

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Problem statement/ aim of the experiment / hypothesis and variable can be concludedfrom the situation given. State all the variables Manipulated variable : Responding variable :

Constant variable : list down all the fixed variables to ensure the outcome of theresponding variableis related only to the manipulated variables. Separate the substances and apparatus Procedure : All the steps taken in the procedure must include the apparatus used, quantity and type ofsubstance ( powder, solution, lumps etc).

PAPER 31. The diagram below shows the apparatus set-up for the experiment to determine the freezingpoint of

substance X.

The diagram below shows the thermometer reading for the cooling of substance X atcertain time intervals.

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thermometer

Substance X

Volumetric flask

90

95

85

0 Minute1st minute

2nd Minute 3rd minute

85

90

80

85

90

80

85

90

80

85

90

85

90

80

75

80

70

70

75

65

4th minute5th minute

6th minute 7th Minute


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(a) Record the thermometer readingsshown in the diagram above by completing the table below.(3 marks)

(b) Draw the graph of temperatureagainst time on the graph paper provided.

[3 marks](c) Based on the graph in (b),

(i) State the change in temperature of substance X for the whole experiment.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................[3 marks]

(ii) State the inference for your answer in (c) (i) .

...........................................................................................................................

...........................................................................................................................[3 marks]

(d) What is the freezing point of

substance X? Show and label it on the graph how you obtained the answer.

.............[3 marks]

(e) Based on this experiment, what ismeant by freezing point?

...

time/minute 0 1 2 3 4 5 6 7

Temperature/ oC

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...[3 marks]

(f) If substance X is heated from roomtemperature until 100oC, what is the temperature when substance X starts to melt?Explain your answer.

.......................[3 marks]

3

An experiment is carried out to investigate the statement above.The table below shows theapparatus set up and the observations for the experiment to determine the reactivity of theGroup 1 elements based on their reactions with water.

Apparatus set-up Observation towards the metal

Lithium moves slowly on the surface of the waterwith a hiss sound.

Potassium moves vigorously and randomly on thesurface of the water with a hiss sound.

Sodium moves quickly and randomly on thesurface of the water with a hiss sound.

(a) State the variables that are involved in the experiment.

Name of variables Action to be taken

(i) Manipulated variable:

..

..

(i) The way to manipulate variable:

..

...

(ii) Responding variable:

(ii) What to observe in the responding variable:..

..

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Elements in Group 1 of the Periodic Table of Elements can be arranged based on thereactivity of the elements with water.

water

water

))

sodium

)) )

)))

Potassium

)) ) )

water

Lithium


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(iii) Controlled variable:

..

..

(iii) The way to maintain the controlled variable:

[6 marks]

(b) State one hypothesis for the experiment.

[3 marks]

(c) Based on the observations in the figure above, arrange lithium, potassium andsodium in the descending order of reactivity of metals towards water.

Descending order of reactivity of metals towards water.[3 markah]

(d) Solution X was produced from the reaction of sodium with water. Classify the ionsthat exist in solution X into positive ions and negative ions.

Positive Ions Negative Ions

[3 marks]

( Paper 3 )

1

Covalent compounds are non-conductors of electricity in any state. Ioniccompounds can conduct electricity when dissolved in water.

Referring to the above statement, design a laboratory experiment related to the electricalconductivity of ethanol and aqueous sodium nitrate solution.

In designing your experiment, the following aspects mustbe included :a) Problem statementb) Hypothesisc) List of substances and apparatusd) Experimental procedurese) Results

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[Ans] :

a) Problem statement :

b) Hypothesis : . does not conduct electricity

whereas .

conducts electricity.

c) Substances :

Apparatus : beaker .. cm3 , measuring cylinder ...

cm3

, . , .light bulbs, switch, connecting wires with clips,

d) Experimental procedure :

1. . of ethanol is measured by a measuring

cylinder and is poured into a beaker.

2. Two rods are immersed in ethanol and

the circuit is completed by connecting to batteries, a switch and

a light bulb.

3. The switch is turned on and the bulb is checked if it is

4. The experiment is repeated by using e) Results

Chemicalcompound

Observation

Ethanol

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When lithium metal is put in water, it moves very slowly on the surface of the water. When sodiummetal is put in water, it moves quite fast and produces hiss sound. When potassium metal is put inwater, it moves very fast and produces small explosions.

Metal

AqueoussodiumNitrate solution

2

Plan an experiment in the laboratory to investigate the reactivity of lithium, sodium and potassiumwith water and describe the effect of the solution produced towards a red litmus paper.The planning of your experiment must consist of the following:

(a) Aim of experiment(b) Statement of the hypothesis(c) All the variables(d) List of substances and apparatus(e) Procedure of the experiment(f) Tabulation of data

[17 marks]

QUESTIONS END

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Water

Common Mistakes for Paper 2 and 3

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