QUESTION 1



Grade 12

PHYSICAL SCIENCES - CONTROL TEST

Time: 40 minutes Marks: 50

QUESTION 1

There are four possible options for each answer in the following questions. Each question has only ONE correct answer. Choose the correct answer and write only A, B, C or D next to the question number.

1.1 Consider the following two balanced chemical equations.

|SO2 (g) |+ |2H2S (g) |( |3S (s) |+ |2H2O (l) |

|SO2 (g) |+ |Mg (s) |( |S (s) |+ |2MgO (s) |

The reducing agent(s) in these two reactions is (are) …

A only SO2

B SO2 and Mg

C H2S and Mg

D SO2 and H2S (2)

1.2 Different structural forms of the same compound are …

A isotopes

B isobars

C allotropes

D isomers (2)

[4]

QUESTION 2

Give one word or term for each of the following descriptions. Write only the word or term next to the question number.

2.1 The gain of electrons by an atom, ion or molecule (1)

2.2 A large molecule that is composed of many smaller repeating units (1)

2.3 Hydrocarbons in which each carbon atom is bonded to four other atoms (1)

[3]

QUESTION 3

We can separate crude oil into more usable fractions. Naphtha is a fraction of crude oil that consists of hydrocarbons with six to ten carbon atoms. An example of one of these hydrocarbons is decane. The following equation shows the reaction in which we break down decane into smaller molecules.

|decane |( |pentane |+ |propene |+ |ethene |

3.1 Name the process that we use to break down decane into simpler compounds. (1)

3.2 Write the molecular formula of pentane. (2)

3.3 Write the structural formula of ethene. (2)

3.4 Ethene molecules can join together to form long chains. Name this process. (1)

3.5 Name the substance produced when ethene molecules join together to form long chains. (1)

3.6 Identify ONE commercial use of this long-chain product. (1)

[8]

QUESTION 4

Consider the equation for the reaction between zinc metal and a copper(II) sulfate solution.

|Zn |+ |CuSO4 |( |Cu |+ |ZnSO4 |

4.1 Write the equation for the oxidation half reaction. (2)

4.2 Write the equation of the half reaction for the reducing agent. (2)

4.3 Identify the oxidising agent. (2)

[6]

QUESTION 5

The alkenes are a homologous series of unsaturated hydrocarbons.

5.1 Define the term unsaturated. (2)

5.2 Write the general formula of the alkenes. (2)

5.3 Draw the structural formula of the simplest alkene. Name this alkene. (3)

5.4 Patricia shows the difference between the reaction of an alkane, cyclohexane, and an alkene, cyclohexene, in her school laboratory. State the substances she used and the results she observed. (3)

[10]

QUESTION 6

Methane gas reacts with chlorine gas in the presence of light. The following equation describes the reaction.

|CH4 |+ |Cl2 |( |CH3Cl |+ |HCl |(H = –99,5 kJ |

6.1 Decide whether this reaction is endothermic or exothermic. (1)

6.2 Explain how you reached your decision in question 6.1. (2)

6.3 Draw an energy profile diagram for this reaction. On your diagram, clearly indicate the reactants and products, the activation energy, the enthalpy change and the activated complex. (6)

[9]

QUESTION 7

Methyl ethanoate is an ester.

7.1 Draw the structural formula of methyl ethanoate. (2)

7.2 Write down the names of the acid and alcohol needed to make methyl ethanoate. (2)

Another ester and an acid are isomers of methyl ethanoate.

7.3 What do you understand by the term “isomer”? (2)

7.4 Write down the name and structure of the isomer. (3)

7.5 Give the chemical formula of the acid. (2)

[11]

[TOTAL: 50 marks]

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