2007 MRSM P2

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Transcript of 2007 MRSM P2

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    Paper 2 MRSM 2007

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    Section A

    1. Diagram 1 shows the electronic arrangement of atoms of six elements.

    P, Q, R, S, T and U do not represent the actual symbol of the elements. Use the

    letters to answer the following questions.

    Diagram 1

    (a). Determine and fill the position of P and T in the Periodic Table of

    Elements given below.[2M]

    Q R

    S U

    (b) State one element which:

    (i) is a metal : ............................................................................................. [1M]

    (ii) forms an ion with +2 charge : ................................................................ [1M]

    (iii) is used in advertising light: ................................................................... [1M]

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    (c) Name the products formed when S reacts with water.[2M]

    .

    (d) State one usage of U in water treatment plant. [1M]

    .

    (e) The atomic radius of T is smaller than S. Explain why.[1M]

    .

    2. Diagram 2 shows the electrolysis of 1.0 mol dm-3 sodium chloride solution

    which is still in progress.

    Diagram 2

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    (a) Write the formulae of all ions present in the electrolyte. [1M]

    .

    (b) Name the gas produced at:[2M]

    (i) burette X : ......................................................................................................

    (ii) burette Y : .....................................................................................................

    (c)State how you would verify the gas named at b(i).[3M]

    .

    .

    .

    (d) (i) Write the half-equation for the process that occurs in burette X. [1M]

    .

    (ii) At the end of the experiment, 30.00 cm-3 of gas was collected at room

    temperature in burette X.

    Calculate the number of moles of gas collected in burette X.[1 mol of gas occupies a volume of 24.0 dm3 at room temperature]

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    (e) Name a substance that can be used to replace carbon electrodes for the

    experiment to get the same result? [1M]

    .

    (f) State one usage of the electrolysis of sodium chloride solution in industry.

    [1M]

    .

    3. (a) Diagram 3 shows a series of tests performed on a colourless solution

    which contains one cation and two anions.

    Diagram 3

    (i) Based on the observations in Diagram 3, complete the table below with

    appropriate inferences.[3M]

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    Test Inference

    1

    2

    3

    (ii) Write an ionic equation for the reaction in Test 3.[1M]

    .

    (b) A student wants to prepare a pure sample of crystalline zinc sulphate by

    reacting dilute sulphuric acid with substance X.

    (i) Name the substance X.[1M]

    .

    (ii) Write an equation for the above reaction.[1M]

    .

    (iii) Calculate the maximum mass of zinc sulphate that can be prepared if

    50.0 cm3of 0.2 mol dm-3sulphuric acid is reacted with excess X. [3M]

    [The relative formula mass of zinc sulphate = 161]

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    4. An experiment is carried out to study the effect of concentration on rate of

    reaction.

    50.0 cm3of 0.5 mol dm-3hydrochloric acid and excess granulated calcium

    carbonate is put into a conical flask and is placed on an electronic balance

    as shown in Diagram 4.The mass of the conical flask and its contents is recorded at 60 seconds

    intervals.

    Diagram 4

    Table 4 shows the results.

    Time/s. 0 60 120 180 240 300 360 420 480

    Balance readings/g 140.64 140.48 140.37 140.31 140.26 140.22 140.20 140.20 140.20

    Table 4

    (a) Give the definition of rate of reaction. [1M[

    .

    (b) Explain why the mass of the conical flask and its content decreases with

    time. [1M]

    .

    .

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    (c) Based on Table 4, plot a graph of the mass of the conical flask and its

    content versus time on the graph paper below. [3M]

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    (e) (i) Calculate the mass of carbon dioxide gas produced. [1M]

    (ii) Calculate the expected volume of gas produced at room condition.

    [1 mol of gas occupies 24 dm3

    at room condition; relative molecular mass ofCO2is 44]

    5. Diagram 5 shows a series of chemical reactions starting from compound Y.

    Diagram 5

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    (a) Name compound Y. [1M]

    .

    (b) Draw a diagram to show the set-up of apparatus if Process I is to be carried

    out in a laboratory. [2M]

    Name of compound P : .........................................................

    (d) Describe how Process III could be done in a laboratory. [3M]

    .

    .

    .

    (e) (i) Name the process that occurred. [1M]

    .

    (ii) Write a chemical equation for the above reaction. [2M]

    .

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    6. In an experiment to study the heat of neutralization, 25.0 cm3 of a 1.0

    mol dm-3 sodium hydroxide solution was added to 25.0 cm-3 of a 1.0 mol dm-3

    aqueous hydrochloric acid. The mixture was then stirred and the maximum

    temperature was recorded.

    Diagram 6 shows the set up of the apparatus used in the experiment.

    Diagram 6

    The following data was obtained.

    Initial temperature of sodium hydroxide solution = 28.5C

    Initial temperature of hydrochloric acid solution = 28.5C

    Maximum temperature of the mixture = 34.5C

    (a) What is meant by heat of neutralization? [1M]

    .

    (b) Write an ionic equation for the reaction between hydrochloric acid and

    sodium hydroxide. [1M]

    .

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    (c) Based on the data obtained from the experiment, calculate

    (i) the number of moles of hydrochloric acid used. [1M]

    (ii) the amount of heat released [1M]

    (iii) the heat of neutralization [1M]

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    (d) Draw the energy level diagram for the reaction.[2M]

    (e) (i) The heat of neutralization obtained from the experiment is less than the

    theoretical value. Give a reason. [1M]

    .

    .

    (ii) Suggest one step that should be taken to modify the apparatus in order to

    get a more accurate result. [1M]

    .

    .

    (f) The experiment is repeated by doubling the volume of both hydrochloric

    acid and sodium hydroxide. Assuming the initial temperature is maintained,

    what would be the maximum temperature of the mixture?

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    Section B

    7. (a) Table 7.1 shows information on the atomic structure and the relative

    atomic mass of three elements: aluminium, carbon and oxygen.

    Element Number of proton Number of neutron Relative atomic mass

    Carbon 6 6 12

    Oxygen 8 8 16

    Aluminium 13 14 27

    Table 7.1

    (i) Based on Table 7.1, state the relationship between the relative atomic

    mass of an element with the number of proton and neutron of its atom. [1M]

    (ii) Draw the electronic arrangement diagram for an ion of oxygen. [2M]

    (iii) Aluminium and carbon react with oxygen to form aluminium oxide and

    carbon dioxide respectively. The reactions are represented by the following

    equations.

    I. 4 Al + 3O2 2 Al2O3

    II. C + O2 CO2

    Describe how chemical bonds in aluminium oxide and carbon dioxide are

    formed. [8M]

    (b) Naphthalene and sodium chloride are white crystals at room temperature.

    Table 7.2 shows two physical properties of the compounds.

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    Compound Melting point /C Electrical conductivity

    Naphthalene 80 Non electrolyte

    Sodium chloride 801 Electrolyte

    Table 7.2

    Explain the differences in the melting points and the electrical conductivity of

    naphthalene and sodium chloride.

    Your answer should be based on the [5M]

    o types of particles present in both compoundso types of bonds ando forces of attraction

    (c) Diagram 7 shows the symbol of two atoms of oxygen.

    Diagram 7

    Compare and contrast the two atoms of oxygen.[4M]

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    8. (a) Table 8 shows the pH of two solutions.

    Solution pH

    0.1 mol dm-3 of potassium hydroxide solution 13

    0.1 mol dm-3 of aqueous ammonia 11

    Table 8

    Explain why the two solutions have different pH. [4M]

    (b) An unlabeled reagent bottle is said to contain sulphuric acid solution.

    Describe how you would confirm the solution. [4M]

    (c) The structural formula of ethanoic acid is shown in Diagram 8.

    Diagram 8

    (i) Explain why ethanoic acid is a monoprotic acid. [2M]

    (ii) Glacial ethanoic acid does not conduct electricity but the aqueous solution

    of ethanoic acid does. Explain why.[3M]

    (iii) When zinc powder is added into an aqueous ethanoic acid, bubbles of

    colourless gas are evolved.

    Write a chemical equation for the reaction.[2M]

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    Explain how zinc and tin layers in P and Q protect the iron bars from corrosion.

    Determine which iron bar is