Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2013 Summer Zone 1

The electronic structures of five atoms of different elements, A, B, C, D and E, are shown below:



Answer the following questions about these structures. Each structure may be used once, more than once or not at all.

(a) Which structure

(i) is in Period 4 of the Periodic Table, □

(ii) is a noble gas, □

(iii) is in Group II of the Periodic Table, □

(iv) has five electrons in its outer shell, □

(v) has a proton (atomic) number of 7, □

(vi) represents a fluorine atom? □

[6]

(b) Complete the following sentences about elements using words from the list below.

alkali atom covalent ion
monatomic three transition two

An element is a substance containing only one type of ........................... .
The Group VII elements exist as molecules containing ........................... atoms.
Carbon has a giant ........................... structure with many strong bonds.
Elements such as iron and copper, which form coloured compounds, are called ........................... elements.

[4]

The table below shows some properties of the Group I elements.

[Table_1]

(a) Use the information in the table to explain why caesium is a liquid when the temperature is 34°C.
...............................................................................................................................
............................................................................................................................... [1]

(b) Suggest a value for the boiling point of potassium.
.................. °C [1]

(c) (i) Describe the general trend in density down the group.
............................................................................................................................... [1]
(ii) Which element does not follow this trend?
............................................................................................................................... [1]

(d) State three physical properties of potassium, other than density, melting point and boiling point.
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............................................................................................................................... [3]

(e) Potassium reacts with water. The products are potassium hydroxide and hydrogen.

(i) Describe two observations when potassium reacts with water.
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...............................................................................................................................
............................................................................................................................... [2]
(ii) Complete the symbol equation for this reaction.

$$2K + \text{......}H_2O \rightarrow 2KOH + \text{......}$$ [2]

(a) Match the name of the homologous series on the left with its formula on the right. The first one has been done for you.

halogenoalkane .................................... $\text{C}_2\text{H}_6$
alkane .................................... $\text{CH}_3\text{COOH}$
alkene .................................... $\text{C}_2\text{H}_5\text{OH}$
alcohol .................................... $\text{C}_2\text{H}_5\text{Cl}$
carboxylic acid .................................... $\text{C}_2\text{H}_4$
[4]

(b) Draw the full structural formula of the compound, $\text{C}_2\text{H}_6$, showing all atoms and bonds.
[1]

(c) The compound with the formula $\text{C}_2\text{H}_4$ is an unsaturated hydrocarbon.
Describe the difference between a saturated and an unsaturated hydrocarbon in terms of the bonds they contain.
..........................................................................................................................
..........................................................................................................................[2]

(d) Describe a test to distinguish between a saturated and unsaturated hydrocarbon.
test .....................................................................................................................
result with saturated hydrocarbon .........................................................................
..........................................................................................................................
result with unsaturated hydrocarbon .................................................................
..........................................................................................................................[3]

(a) Why do farmers use fertilisers? In your answer, include
• the names of the essential elements present in most fertilisers,
• the reasons why farmers use fertilisers.
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................................................................................................................................. [4]

(b) Urea can be used as a fertiliser.
The structure of urea is shown below.


(i) Deduce the molecular formula of urea.
................................................................................................................................. [1]

(ii) Calculate the relative molecular mass of urea. You must show all your working.
................................................................................................................................. [2]

(c) Urea is a solid at room temperature. Complete the diagram below to show the arrangement of the molecules in solid urea.
Show a molecule of urea as ○

[2]

(d) When urea is heated with an alkali, ammonia is given off.
Describe a test for ammonia.
test .................................................................................................................................
result ................................................................................................................................. [2]

The table shows some properties of four substances, A, B, C and D.

[Table_1]

(a) Which one of these substances has
(i) a giant covalent structure,
(ii) a simple molecular structure,
(iii) a metallic structure? [3]

(b) A student carried out an experiment to determine the rate of reaction of calcium carbonate with excess hydrochloric acid.

$ \text{CaCO}_3(s) + 2HCl(aq) \rightarrow \text{CaCl}_2(aq) + \text{CO}_2(g) + \text{H}_2\text{O}(l) $

He recorded the loss of mass of the reaction mixture over a period of time.



(i) Explain why the reaction mixture decreases in mass. [1]
........................................................................................................
(ii) At what time has the reaction just finished? [1]
.................. s
(iii) From the graph, deduce the loss in mass in the first 100 seconds. [1]
................. g
(iv) The student repeated the experiment keeping everything the same except for the size of the pieces of calcium carbonate. He used smaller pieces of calcium carbonate but the mass used was the same.
On the grid above, draw a line to show how the loss of mass changes with time when smaller pieces of calcium carbonate are used. [2]
(v) State the effect of increasing the concentration of hydrochloric acid on the rate (speed) of this reaction when all other factors remain constant. [1]
........................................................................................................

(a) Propanol is a solvent.
Sugar is soluble in propanol. Salt (sodium chloride) is insoluble in propanol.
A student wants to separate a mixture of solid salt and solid sugar.

(i) Describe how she could separate the salt from the sugar.
You may draw a labelled diagram to help you answer this question.

(ii) Describe how the student could obtain solid sodium chloride from a solution of sodium chloride in water.

(b) The diagram shows the structure of sodium chloride.

(i) Deduce the simplest formula for sodium chloride.

(ii) What type of bonding is present in sodium chloride?
Put a ring around the correct answer.
covalent ionic metallic weak

(c) The diagram shows the apparatus used to electrolyse a concentrated aqueous solution of sodium chloride.

(i) Which letter on the diagram, A, B, C or D, represents the electrolyte?

(ii) Name the product formed at
the positive electrode, ...........................................................
the negative electrode. ...........................................................

(a) A student set up the apparatus shown below.
The concentrated hydrochloric acid gives off hydrogen chloride gas.
After 15 seconds, the damp blue litmus paper begins to turn red.
After 25 seconds, the litmus paper has turned completely red.

Use ideas about moving particles to explain these observations.
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....................................................................................................................... [4]

(b) Hydrogen chloride reacts with ammonia to form a salt which has the formula $\text{NH}_4\text{Cl}$.
State the name of this salt.
....................................................................................................................... [1]

(c) (i) Hydrochloric acid reacts with iron to form iron(II) chloride and hydrogen.
Write a word equation for this reaction.
....................................................................................................................... [1]

(ii) Describe a test for iron(II) ions.
test .......................................................................................................................
result ....................................................................................................................... [2]

(d) A student investigates various methods of protecting iron from rusting. She sets up four tubes as shown in the diagram below.

(i) Tube 1 contains unprotected iron. What is the purpose of this experiment?
....................................................................................................................... [1]

(ii) State the names of the two substances needed for iron to rust.
......................................... and ......................................... [2]

(iii) Explain why the iron in tube 4 does not rust.
.......................................................................................................................
....................................................................................................................... [1]

(iv) Explain why the iron in tube 3 eventually rusts.
.......................................................................................................................
....................................................................................................................... [1]

The diagram shows a silvered light bulb.

Some properties of metals used in the light bulb are shown in the table below.
[Table_1]
(a) (i) Suggest why copper rather than tungsten is used for electrical wiring?
......................................................................................................................................... [1]
(ii) Suggest why silver is not used for electrical wiring.
......................................................................................................................................... [1]
(iii) Suggest two reasons why tungsten rather than copper is used to make the bulb filament.
reason 1 .................................................................................................................................
reason 2 ................................................................................................................................. [2]
(iv) Explain why the copper wires are covered with plastic.
.........................................................................................................................................
......................................................................................................................................... [2]

(b) Brass is an alloy. Which one of the following diagrams, A, B, C or D, best represents an alloy?

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