Miracle Learning Centre (O Level Chemistry Tuition/ IP Chemistry Tuition) Are you able to answer this Chemistry Tuition Question?

10 Nov Miracle Learning Centre (O Level Chemistry Tuition/ IP Chemistry Tuition) Are you able to answer this Chemistry Tuition Question?

Question 1

  1. Hydrogen peroxide can behave as an oxidizing agent and reducing agent. Study the observations given in the table below and deduce whether hydrogen peroxide functions as an oxidizing or reducing agent.
    Reaction of hydrogen peroxide with iodine solution Reaction of hydrogen peroxide with iron (II) sulphate solution
    Observation Brown solution turns colourless Pale green solution turns yellow
    Function of hydrogen peroxide
  2. Potassium dichromate (VI) has the following structure :
    potassium-dichromate
    What is the total number of electrons in the covalent bonds surrounding one chromium atom?
  3. Sulphur dioxide, an air pollutant is detected by bubbling the polluted air through an aqueous solution of potassium dichromate (VI). A change in colour from orange to green confirms its presence. The ionic equation is shown below.
    3SO2 + Cr2O72- + 2 H+ → 3 SO42- + 2 Cr3+ + 3H2O
    1. State two properties from this reaction which shows that chromium is a transition metal.
    2. Which substance is a reducing agent? Explain your answer in terms of the change in oxidation state.

Question 2

The following information is given for the chlorides of some elements in Period 3. The elements are labelled W, X, Y and Z. (You need not identify W, X, Y and Z)

Element Formula of chloride Melting point /oC Boiling point / oC Behaviour with water
W WCl2 714 1418 Soluble, forming a colourless solution
X XCl 790 1407 Soluble, forming a colourless solution
Y YCl4 – 70 58 Soluble, forming a colourless solution that turns blue litmus red.
Z Z2Cl2 – 80 138 Forming a yellow precipitate and a colourless solution that turns blue litmus red.
  1. Arrange the elements W, X, Y and Z in order of increasing atomic number.
  2. Which of these elements are likely to be non-metals?
  3. State one difference each in physical and chemical properties between chlorides of metals and those of non-metals.
  4. Which element would you expect to form a basic oxide readily soluble in water? Explain your answer.

Question 1

    1. Explain the term polymerization.
    2. State 2 differences between addition polymerisation and condensation polymerisation.
    3. Give one named example of an addition polymer and a condensation polymer. State a use for each.
      Type of polymer Named example Use
      Addition
      Condensation
  1. Plastics are man-made polymers which have become indispensable in our daily lives. Explain how plastics can be a source of both air and land pollution.

Miracle Learning Centre (O Level Chemistry Tuition/ IP Chemistry Tuition)
Did you answer the Chemistry Tuition Question correctly?

Question 1

  1. Reaction of hydrogen peroxide with iodine solution Reaction of hydrogen peroxide with iron (II) sulphate solution
    Observation Brown solution turns colourless Pale green solution turns yellow
    Function of hydrogen peroxide Reducing Agent (1m) Oxidising agent (1m)
  2. 12 electrons
    1. It has variable oxidation states ( +6 and +3).
      It forms coloured salt solution ( orange / green )
    2. Reducing agent is SO2
      Cr2O72- is reduced because the oxidation state of Chromium is decreased from +6 to +3.

Question 2

  1. X, W, Y and Z
  2. Y and Z
  3. Chlorides of metals have high melting/boiling points whereas chlorides of non-metals have low melting/boiling points. Chlorides of metals do not form acidic solution when dissolves in water but chlorides of non-metals dissolves in water to form acidic solution.
  4. Element X. X is in Group I, it will behave similarly as sodium and potassium. They react with oxygen to form basic oxides that are soluble in water.

Question 3

    1. Is the process in which many small molecules (monomers) are linked together by covalent bonds to form a giant molecule
    2. Addition Polymerisation:
      Monomers are unsaturated
      There is no loss of small molecules / atoms
      Condensation polymerization:
      Monomers must have 2 functional groups
      There is a loss of simple molecules such as water.
    3. Type of polymer Named example Use
      Addition Polyethene (1/2m) Used to make ….. (1/2m)
      Condensation Nylon OR Terylene (1/2m) Used to make …… (1/2m)
  1. Plastic are non-biodegrable.
    When discarded, they do not decompose but remain unchanged and so is a source of land pollution – breeding ground for mosquitoes.
    When burnt, plastics produce poisonous fumes such as carbon monoxide, causing air pollution.

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