nhhs 2012 chemistry prelim 1 p2

Nan Hua High School 2012 Preliminary Examinations Chemistry 5072/02

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Name: _________________________ ( ) Class: _________

Subject : Chemistry

Paper : 5072/02

Level : Secondary Four Express

Date : 28 June 2012

Duration : 1 hour 45 minutes

INSTRUCTIONS TO CANDIDATES

Write your name, class and index number on the cover page. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working.

Do not use staples, paper clips, highlighters, glue or correction fluid.

SECTION A Answer all questions in the spaces provided.

SECTION B

Answer all three questions, the last question is in the form either/or. Write your answers on the lined paper provided and if necessary, continue on separate answer paper.

INFORMATION FOR CANDIDATES

At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 21. The total of the marks for this paper is 80.

This paper consists of 21 printed pages.

For Examiners Use

Section A /40

Section B /50

B 10 /10

B 11 /10

B 12 /10

Total /100

NAN HUA HIGH SCHOOL

2012 PRELIMINARY EXAMINATIONS


Page 2 of 21

Section A

Answer all the questions in this section in the spaces provided. The total mark for this section is 50.

A1 The table below gives information about five substance, A to E.

Substance Melting point

(C)

Boiling point

(C)

Solubility in

water

A -272 -269 insoluble

B -114 78 soluble

C 1326 2000 insoluble

D -71 99 insoluble

E 770 1420 soluble

a) At room temperature and pressure, which of the following substance (s)

is/are

i) liquid(s)?

_________________________________________________________

[1]

ii) gas(es)?

_________________________________________________________

[1]

b) Describe the arrangement and movement of particles of substance D

when it is at -80C.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

[2]


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c) Both substance C and E would not decompose upon heating.

Suggest how you could separate a mixture of substance C and E to

produce a sample of each.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

[2]

Total: [6]

A2 The diagram below shows the arrangement of particles in four different

substances A, B, C and D at room temperature.

a) i) Which of these substances has the lowest melting point?

_________________________________________________________

[1]


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ii) Explain why this substance has a low melting point in terms of bonding

and structure.

_________________________________________________________

_________________________________________________________

_________________________________________________________

[2]

b) i) At high temperature, another of these substances will conduct

electricity. Which substance is this?

_________________________________________________________

[1]

ii) Explain why this substance only conducts electricity at high

temperature but not at room temperature.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

[2]

Total: [6]


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A3 The diagram below shows the structure of an atom of the element E.

a) Complete the table below about the three different particles found in an atom of element E.

[3]

b) Draw a dot and cross diagram showing only the outer electrons in a

molecule of HE.

[2]

Total: [5]


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A4 Some sweets and candies are coloured red by a mixture containing several dyes. Chromatography was carried out to analyse the mixture and the solvent used is water.

a) Why did the orange dye in the mixture travel further than the red dye?

__________________________________________________________

__________________________________________________________

[1]

b) In preparing the chromatogram, the following instructions were given. Suggest a reason for each instruction:

i) The starting line should be drawn with a pencil rather than with ink. __________________________________________________________

__________________________________________________________

[1]

ii) At the end of the experiment, the solvent front should be near the top of

the paper. __________________________________________________________

__________________________________________________________

[1]

Total: [3]

solvent front

orange spot

yellow spot

red spot

light orange spot

lid

beaker

strip of filter paper

position of red spot at

start of experiment

solvent


Page 7 of 21

A5 Sulfuric acid is a strong acid and is used in the manufacturing of fertilisers.

a) What do you understand by the term strong acid?

__________________________________________________________

__________________________________________________________

[1]

b) A student wrote this as his answer: when water is added to sulfuric acid,

it becomes a weak acid. Is this answer correct? Suggest a reason for

your answer.

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

[2]

c) Lead(II) sulfate is formed on electrodes when car batteries are

discharged.

i) Given that car batteries contain sulfuric acid, suggest the other substance that causes the formation of lead(II) sulfate. __________________________________________________________

[1]

ii) Write down the ionic equation for the above reaction.

__________________________________________________________

[1]

Total: [5]


Page 8 of 21

A6 The table below shows the results of an experiment using 0.10 g of

magnesium ribbon and 25 cm3 of 2.0 mol/dm3 sulfuric acid. In the

experiment, magnesium ribbon was mixed with dilute sulfuric acid and the

total volume of hydrogen produced was measured every five seconds. After

fifty seconds, the reaction had stopped.

time from start of experiment / s total volume of hydrogen produced / cm3

0 0 5 31 10 54 15 71 20 85 25 94 30 99 35 100 40 100 45 100 50 100

a) Calculate the number of moles of magnesium and of sulfuric acid used in

the experiment.

[1]

b) The experiment was repeated using the same mass of magnesium but

25 cm3 of 3.0 mol/dm3 sulfuric acid. State and explain how the initial rate

of formation of hydrogen compared with the original experiment.

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

[2]


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c) The experiment was repeated for a third time using 25 cm3 of 3.0

mol/dm3 hydrochloric acid. State and explain how the initial rate of

formation of hydrogen compared with the experiment in (b).

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

[2]

Total: [5]

A7 Ammonia and carbon dioxide react to form water and a gas, urea, CON2H4. In the reaction, 240 dm3 of ammonia and 84 dm3 of carbon dioxide are reacted at room temperature and pressure, (r.t.p) to form urea.

a) Write the equation, including state symbols, for the formation of urea.

__________________________________________________________

[2]

b) Calculate the volume of ammonia which reacted.

[2]

c) Calculate the total volume of gas at the end of the reaction.

[2]


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The bags of ammonium nitrate fertiliser have the following warning printed on them. The main lime-containing product used on farms is calcium hydroxide.

d) Why is calcium hydroxide added to soils?

__________________________________________________________ __________________________________________________________

[1]

e) Why is it important not to add ammonium compounds to soils that have

been treated with calcium hydroxide? __________________________________________________________ __________________________________________________________ __________________________________________________________

[1]

Total: [8]

Do not add fertiliser to soil that

has been recently treated with

any lime-containing product.


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A8 The table shows the composition of the atmosphere of the planet, Mars.

Gas Percentage composition

Argon 1.4 %

Oxygen 1.6 %

Nitrogen 3.3 %

Other gases 2.5 %

Carbon dioxide 91.2 %

a) How does the atmosphere on Mars differ from the atmosphere on Earth?

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

[3]

b) Scientists predicted the surface temperature on Mars by calculating its

distance from the Sun. The measured surface temperature is slightly

higher than the predicted value. Based on the table, suggest why is this

so?

__________________________________________________________

__________________________________________________________

__________________________________________________________

[1]


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c) Carbon dioxide on Earth is regulated by processes such as photosynthesis and dissolution of carbon dioxide in water. Suggest why the amount of carbon dioxide in the atmosphere will increase when the global temperature is high. __________________________________________________________ __________________________________________________________

[1]

d) Trace amount of carbon monoxide has also been found in the

atmosphere on Mars. Carbon monoxide is an air pollutant on Earth and a health hazard. Explain why the gas is a health hazard. __________________________________________________________ __________________________________________________________

[1]

Total: [6]

A9 Ethanal can be used as the starting material for the preparation of an ester. The steps can be summarized as follows:

a) State the reagent and conditions needed for Step 1 and identify the type

of reaction occurring.

__________________________________________________________

[2]

b) Name the other organic compound needed for Step 2 and state the

reagent(s) and conditions for its formation.

___________________________________________________________

___________________________________________________________

[3]

c) Name the ester formed in the above process and state a use for it.

___________________________________________________________ ___________________________________________________________

[2]

Total: [7]

END OF SECTION A


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Section B

Answer all three questions from this section. The last question is in the form

either/or and only one of the alternatives should be attempted.

B10 The metal tungsten, symbol W, is used to make wire filaments in light bulbs. The wire glows when electricity passes through it.

a) Draw a labelled diagram to show the structure of tungsten metal. [2]

b) Tungsten typically combines with oxygen to form a yellow compound, tungsten (VI) oxide.

i) Write an equation for the reaction between tungsten and oxygen. [1]

ii) Explain why this is a redox reaction in terms of oxidation states. [2]

iii) Tungsten (VI) oxide can be dissolved in aqueous alkaline solution

to form tungstate ions, WO42- . State the oxidation state of tungsten

in tungstate ion.

[1]

c) The table below shows the reaction of various metals with dilute hydrochloric

acid.

Metal Reaction Maximum temperature reached / oC

A No bubbles at all 30

Iron Slow bubbling 50

B Very slow; only a few bubbles seen

34

C Slow bubbling 42

D Vigorous bubbling 82

Aluminium No bubbles at the start then rapid bubbling

64

E Steady bubbling 58

i) From these results, arrange the metals in order of decreasing reactivity.

[1]

ii) Explain the observations for the reaction involving aluminium. [3] Total: [10]


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B11 Given the structures of the repeating units of the polymers below, draw the full structural formula of the monomers from which they are formed.

a) i)

[1]

ii) [1]

iii)

[2]

b) Describe the essential differences between the structures of

monomers that form addition polymers and the structures of

monomers that form condensation polymers.

[2]

c) Many organic compounds can exist as isomers. Draw the full

structural formula and name an isomer of ethanoic acid.

[2]

d) Name the reagent and state the conditions required to make

ethanol. [2]

Total: [10]

B12

Either

The table below shows some bond energies, measured in kilojoules per mole. Bond energy is the energy required to break the bonds between pairs of atoms.

bond bond energy in

kJ/mol bond

bond energy in kJ/mol

C H 414 H O 460 O O 142 O = O 499 C C 348 C = C 612 C O 351 C = O 745

a) Is a double bond between two carbon atoms twice as strong as a single bond? Use the information given above to explain your answer.

[2]


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b) Use the information given above to calculate the enthalpy change for the combustion of 1 mole of propene.

[3]

Butane and but-2-ene are both colourless gases.

c) Write a balanced equation for the complete combustion of but-2-

ene.

[1]

d) Describe a chemical test to distinguish but-2-ene from butane. [2] e) CH3COCH3 is the first member of the ketone homologous series.

Draw the full structural formula of the next member of this homologous series and predict how its melting point compares with that of CH3COCH3.

[2]

Total: [10]

B12

OR

A pupil electrolyzed 2.0 mol/dm3 of aqueous copper(II) sulfate using

platinum electrodes. A current of 1 ampere was passed. The graph of gain in mass of the cathode against time is plotted below.

a) Write the ionic equations to represent the reaction at the cathode

and anode.

[2]

b) Describe the appearance of the aqueous copper(II) sulfate using platinum electrodes:

[2]

i) after 5 minutes,

ii) after 40 minutes.

Total mass

of copper

deposited/g

0.2

0.4

0.6

0.8

10 20 30 40 50

Time/minutes

0


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c) State one difference in observation when the platinum anode is replaced by copper.

[1]

d) A new element Dodine, Do is found to have an atomic number greater than iodine but smaller than astatine. Dodine dissolves in water to form a dark brown solution.

What is observed if aqueous sodium dodide is reacted with aqueous chlorine?

[1]

e) Write an ionic equation for the reaction in (d) above. [1]

f) The experiment below shows the reaction between halogen and iron.

The observations of the experiments are shown in the table below.

Halogen Observation

X Iron wool glows less brightly. Brown solids are formed in the reacting tube.

Y Iron wool burns brightly and vigorously. Brown solid are formed in the reacting tube.

Z Iron wool glows brightly and less vigorously. Brown solids are formed in the reacting tube.

Arrange the halogens, X, Y and Z, in the order of increasing reactivity.

[1]

g) Halogen Z is a liquid at room temperature. Identify Z in the Periodic

Table. [1]

h) Brown solids are halides of iron(II). What is the chemical formula

for these brown solid formed when Y reacts with iron? [1]

Total: [10] END OF SECTION B

Halogen gas Excess gas

Iron wool

heat


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For Examiners Use


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For Examiners Use


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For Examiners Use


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nhhs 2012 chemistry prelim 1 p2

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