SET 1 Chemistry Confirm A

Chemistry Confirm ‘A’- SET 1

SECTION AAnswer all questions.

1 Table 1 shows the melting point and electrical conductivity of substances P, Q and R.

Properties

Substance

Melting point /oC

Electrical conductivity

Solid Molten

P 94 Cannot conduct Cannot conduct

Q 782 Cannot conduct Can conduct

R 840 Can conduct Can conduct

TABLE 1

Based on Table 1, answer the following questions..(a) (i) What is meant by melting point ?

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

[1 mark](ii) What is the physical state of substance P at 100oC ?

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

[1 mark](b) State the type of particle in substance

P : ...........................................................

Q : ...........................................................

[2 marks](c) Draw the arrangement of particle in substance R.

[1 mark]

1


(d) State a substance which represents metal.

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

(e) Explain why the melting point of Q is higher than P.

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

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

..............................................................................................................................[2 marks]

(f) Explain why substance Q can conduct electricity in molten state but cannot conduct electricity in solid state.

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

.............................................................................................................................[2 marks]

2 Diagram 1 shows the set-up of the apparatus of an experiment to determine the melting point of solid napthelene.

DIAGRAM 1When the solid napthalene is completely melted, it is cooled to room temperature. The temperature is recorded every 1 minute.

2

Water bath

Boiling tube

Thermometer

Heat

Napthalene


(a) Why is water bath used in the experiment?

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

(b) Give one precaution step that you should take during the cooling process of liquid napthalene.

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

(c) The melting point of napthalene is 78°C

(i) Sketch the cooling curve of napthalene.

[2 marks]

(ii) Sketch the heating curve of napthalene.

[2 marks]

3


3 The diagram below shows the atomic symbol of oxygen.

(a) Define relative atomic mass based on the carbon-12 scale.

..........……………………………………………………….......……………..

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

(b) State the relative atomic mass of this element.

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

(c) Draw the electron arrangement of this element.

[2 marks]

(d) This element exists as a diatomic molecules at room temperature.Draw the particle arangement of the molecules.

[1 mark]

4

O168


(e) 0.91 g aluminium produced 1.7 g aluminium oxide after being heated completely.Detemine the empirical formula of Aluminium oxide.

[Relative atomic mass: Al, 27; O,16]

[3 marks]

(f) Calculate the number of moles of aluminium oxide.

[1 mark]

(g) Calculate the number of aluminium ions in Aluminium oxide.

[1 mark]

4 Diagram 2 shows the set-up of the apparatus of an experiment to determine the empirical formula of magnesium oxide.

DIAGRAM 2

Results : Mass of crucible + lid = 24.0 gMass of crucible + lid + magnesium ribbon = 26.4 gMass of crucible + magnesium oxide = 28.0 g

5

Magnesium ribbon

lid

Crucible

Tripod stand Heat


(a) What is meant by empirical formula?

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

(b) Base on the information given:

(i) Calculate the mass of magnesium and the mass of oxygen that have reacted.

[2 marks]

(ii) Calculate the ratio of the number of moles of magnesium atoms to oxygen atoms.[Relative Atomic Mass: O,16; Mg, 24]

[1 mark]

(iii) Determine the empirical formula of magnesium oxide.

[1 mark]

(iv) Write the chemical equation for the reaction in the experiment.

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

(c) Why was the magnesium ribbon cleaned with sand paper before it was heated?

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

(d) Why was the crucible lid opened once in a while during the experiment?

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

(e) State another metal that can be used to replace magnesium ribbon.

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

5 An experiment of the reaction between copper oxide and hydrogen is carried out to determine the empirical formula of copper oxide.

Results:Mass of combustion tube + asbestos paper : 36.20 gMass of combustion tube + asbestos paper + copper oxide : 39.40 gMass of combustion tube + asbestos paper + copper : 38.76

g

(a) What is the colour of copper(II) oxide?

……………………………………………………………………………………… [1 mark]

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

[2 marks]

(c) State one precaution step while doing the experiment.

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

7


(d) Based on the above results,(i) calculate the mass of copper and the mass of oxygen that have reacted.

[1 mark]

(ii) Calculate the mole ratio of copper atoms to oxygen atoms.(Relative Atomic Mass: O, 16; Cu, 64)

[1 mark](iii) Write the empirical formula of copper oxide.

[1 mark]

(e) Write the chemical equation for the reaction in the experiment.

………………………………………………………………………………………[1 mark]

(f) Is the empirical formula of magnesium oxide can be determine by using the same experiment as above? Explain.

………………………………………………………………………………………

………………………………………………………………………………………

………………………………………………………………………………………[2 marks]

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6 Table 2 shows the proton and nucleon number of atoms P, Q and R.

Atom Proton number Nucleon numberP 6 12Q 6 14R 7 14

TABLE 2

Using the information given, answer the following questions:(a) What is meant by

(i) Proton number

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

(ii) Nucleon number

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

(b) (i) State the atoms that are isotope.

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

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

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

(c) How many electrons and neutrons are there in atom R.

…………………………..................…….........…………………………………..[2 marks]

(d) Write the electron arrangement of atom P and R.

P : .......................................................................

R : ...................................................................... [2 marks]

(e) State the number of valence electrons of atom R. ……………………………………………………….........……….................….. [1 mark]

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7 Diagram 3 shows part of the Periodic Table of Elements. A, B, C, D, E, F, G and H do not represent the actual symbol of the elements.

A FB D E G

C H

DIAGRAM 3

Using the letters in the Periodic Table of Elements in Diagram 3, answer the following questions.

(a) (i) Choose one element which can react with cold water. ..………………………………………………………………………...

[1 mark] (ii) State whether the solution formed from the reaction in (a)(i) is acidic or alkaline.

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

(iii) Write the chemical equation for the reaction between element in (a)(i) and

water.

..…………………………………………………………………………. [2 marks]

(b) (i) Which element is a transition element?

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

(ii) State one special characteristic of transition elements.

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

(c) State the number of valence electrons of atom G.

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

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(d) State one of the uses of element F.

………………………………………………………………………………… [1 mark]

(e) The electron arrangement of M2+ ion is 2.8. In Diagram 2, mark “M” in the box for the location of M element in the Periodic Table of Elements.

[1 mark](f) What is the particles found in element E at room temperature?

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

(g) By referring to the attraction forces between the particles, explain why E is a gas and H is a liquid at room temperature.

……………………………………………………………………………………

……………………………………………………………………………………

…………………………………………………………………………………… [2 marks]

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SECTION B

1 (a) Argon is used to fill electric bulbs because argon does not react with the white hot tungsten filament.

What is the group number of argon in the Periodic Table of Elements? Explain why argon does not react with hot tungsten filament in term of electron

arrangement. [4 marks]

(b) When a teacher enters a classroom, students sense the smell of perfume. Explain the situation based on the kinetic theory of matter.

[4 marks]

(c) Diagram 1 shows the arrangement of particles for substances P and Q.

DIAGRAM 1

Compare substance P and Q in terms of the arrangement of particles, force of attraction between particles and the energy content of the particles.

[3 marks]

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P Q


(d) Diagram 2 shows the set up of the apparatus to investigate the reaction of chlorine with iron metal.

(i) State two observations while carrying out the experiment. [2 marks]

(ii) The chemical equation for the reaction is as follow:

3Cl2 + 2Fe 2FeCl3

2.8 g of iron wool is completely reacted with chlorine gas.

Calculate the maximum mass of iron(III) chloride formed.[Relative atomic mass of Cl = 35.5 and Fe = 56]

[4 marks]

DIAGRAM 2

Sodium hydroxide solution

Iron wool

Chlorine gas

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2 Table 3 shows the electron arrangement of elements K, L, M and N.

Element Electron arrangementK 2.1L 2.8.1M 2.8.7N 2.4

TABLE 3

(a) Compare the reactivity of element K with element L in reaction with water. .[4 marks ]

(b) State the type of bond formed and explain the formation of bond formed between(i) L and M(ii) M and N

[12 marks ]

(c) State two physical properties of the compound formed in (b)(i).[2 marks ]

(d) Element X is placed between group 2 and group 13 and period 4 in The Periodic Table of Element.State two special characteristic of element X.

[2 marks]

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3 Diagram 4 shows the symbol of elements W, X, Y and Z.

DIAGRAM 4

(a) Write the electron arrangement of atoms W and Z. [2

marks]

(b) State the position of elements X in The Periodic Table of Element.Explain.

[3 marks]

(c) The reaction between atoms of Y and Z forms and ionic compound whereas the reaction between atoms of X and W forms a covalent compound. Based on the above statement, explain how these ionic and covalent compounds are formed.

[10 marks ]

(d) Compare the properties of ionic compound and covalent compound in terms ofboiling point and electrical conductivity. Explain.

[6 marks ]

15

Z34

17 Y24

12 X16

8 W12

6


SECTION C

4 A compound changed from state P to state Q under process I. Diagram 3 shows the arrangement of particles of the compound in state P and state Q.

Table 1 shows the temperature of the compound during process I.

Time (min)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Temperature (oC)

82 80 78 75 75 75 75 75 73 71

TABLE 1

(a) Name process I.Explain why the temperature remains constant from 1.5 minutes to 3.5 minutes. [3 marks]

(b) Table 2 shows the melting point and boiling point of a compound M.

TABLE 2

(i) State the physical state of compound M at 80oC and 280oC.

[2 marks]

Compare the particles of compound M at 80oC to those at 280oC in terms of the arrangement of particles, the movement of particles, the forces of attraction between particles and kinetic energy of particles.

P QDIAGRAM 3

Process I

Melting point (oC) 105

Boiling point (oC) 210

16


[4 marks]

(ii) Describe an experiment to determine the melting point of compound M. Include a sketch of the heating curve and explain how to obtain the melting point of the substance.

[10 marks]

PAPER 3

1 A boiling tube is filled with naphtalene powder. After that, the boiling tube is suspended in a beaker half filled with water as shown in the diagram below.

The naphtalene is stirred continuously. The temperature of the naphtalene are recorded at half minute intervals until the temperature of the naphtalene reaches 90oC.

The table shows the thermometer reading from the experiment to determine the melting points of naphtalene.

Time/second 0 30 90 120 150 180 210 240 270 300Temperature/°C 62.0 66.0 71.0 78.0 80.0 80.0 80.0 80.0

(a) The figure below shows the reading of thermometer at 270 second and 300 second. Write the thermometer reading in the table

270 second 300 second

(b) Based on the table above, plot the graph of temperature against time in the given graph paper.

17

80

90

80

90

ThermometerBoiling tube

Water bath

Heat

Naphtalene


(c) From the graph, state the boiling point of naphtalene

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

(d) The temperature of naphtalene is constant at t = 150 second until 240 second.

Explain.

………………………………….………………..…………………………………

(e) Predict the melting point of naphthalene if salt is added into it.

…………………………………………………………………………………….

(f) The experiment is repeated by replacing napthelene with acethamide to compare the melting point of both substances.

(i) State the

Manipulated variable: ……………………………………………………

Responding variable: …………………………………………………….

Fixed variable : …………………………………………………….

(ii) State the hypothesis of the experiment :

……………………………………………………………………………

……………………………………………………………………………

2

Plan an experiment by using lithium, sodium and potassium in their reaction with water to prove the above statement.Your planning must include the following items:

(a) Problem statement(b) All variables involved(c) Statement of the hypothesis(d) List of materials and apparatus(e) Experimental procedure(f) Tabulation of data

[17 marks]

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The reactivity of the alkali metals increases when going down group I in the Periodic Table of the Elements

SET 1 Chemistry Confirm A

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