Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2010 Summer Zone 1

Choose from the following list of gases to answer the questions.

ammonia carbon monoxide chlorine ethene methane nitrogen nitrogen dioxide oxygen propane

Each gas can be used once, more than once or not at all.

Which gas

(a) is a greenhouse gas produced by the decomposition of vegetation, ........................................................................................................................ [1]
(b) is an alkane, ........................................................................................................................ [1]
(c) reacts with sulfuric acid to form a salt, ........................................................................................................................ [1]
(d) makes up about 20% of the air, ........................................................................................................................ [1]
(e) is a halogen, ........................................................................................................................ [1]
(f) is a hydrocarbon which decolourizes aqueous bromine? ...................................................................................................................... [1]

This question is about hydrogen and some compounds containing hydrogen.
(a) Hydrogen is a gas at room temperature.
Describe the arrangement and motion of the molecules in hydrogen gas.
arrangement ............................................................
motion ............................................................ [2]
(b) Draw the electronic structure of a hydrogen molecule. [1]
(c) The symbols for two isotopes of hydrogen are shown below.
$$\begin{align} ^1_1H    ^3_1H \end{align}$$
(i) What do you understand by the term \textit{isotope}?
............................................................ [1]
(ii) Complete the table to show the number of subatomic particles in these two isotopes of hydrogen.
[Table_1]
[4]
(d) When hydrogen burns, energy is given out.
State the name given to a reaction which gives out energy.
............................................................ [1]

(e) Hydrochloric acid reacts both with metals and with metal carbonates.
(i) A student observed the reaction of hydrochloric acid with four different metals. The student used the same concentration of hydrochloric acid and the same mass of metal in each experiment.
[Table_2]
Use the information in the table to suggest the order of reactivity of these metals.
most reactive ............................ least reactive
[2]
(ii) State the names of the \textbf{three} products formed when hydrochloric acid reacts with calcium carbonate.
............................................................
............................................................
............................................................ [3]

Some pink cobalt chloride was heated gently in a test-tube. The cobalt chloride turned blue. A few drops of water were then added to the blue cobalt chloride. The cobalt chloride turned pink. (a) (i) State the name of this type of reaction. ....................................................................................................................................... [1] (ii) Complete the following sentence. Use words from the list below. alkaline chloride dehydrated hydrated water When ........................................................ cobalt chloride is heated, it loses its ........................................................ of crystallisation and changes colour. [2] (b) Cobalt is a metal. (i) State two physical properties which are characteristic of metals. ....................................................................................................................................... ....................................................................................................................................... [2] (ii) From its position in the Periodic Table predict two physical properties of cobalt in addition to its general metallic properties. ....................................................................................................................................... ....................................................................................................................................... [2] (c) Cobalt(II) oxide is a basic oxide. Predict one chemical property of cobalt(II) oxide. ....................................................................................................................................... [1]

The table shows the mass of various compounds obtained when 500 \text{ cm}^3 of seawater is evaporated.

[Table_1]

(a) Which negative ion is present in seawater in the highest concentration?
.......................................................................................................................... [1]
(b) Write the symbols for the \textbf{two} ions present in potassium bromide.
........................................................... and ........................................................... [1]
(c) Calculate the mass of sodium chloride present in 5 g of the solid left by evaporating the seawater. [1]

(d) Describe a test for iodide ions.
test .................................................................................................................
result ............................................................................................................... [2]

(e) Aqueous chlorine reacts with aqueous sodium iodide.
(i) Complete the equation for this reaction.
\[ \text{Cl}_2 + 2\text{NaI} \rightarrow \text{...........} + 2\text{NaCl} \] [1]
(ii) What colour is the solution when the reaction is complete?
...................................................................................................................... [1]
(iii) An aqueous solution of iodine does not react with aqueous potassium bromide. Explain why there is no reaction.
....................................................................................................................... [1]

(f) Calculate the relative formula mass of magnesium chloride, $\text{MgCl}_2$. [1]

Ammonium sulfate is used in fertilisers.
(a) State the names of the three elements found in most fertilisers.
1. .......................................................
2. .......................................................
3. .......................................................

(b) Suggest why farmers use fertilisers.
........................................................................................................................
........................................................................................................................

(c) Ammonium sulfate is a salt which is soluble in water.
(i) What do you understand by the term $soluble$?
......................................................................................................
(ii) Which of the following methods is used to make this salt in the laboratory?
Tick one box.
adding an acid to a metal [ ]
adding an acid to a metal oxide [ ]
by a precipitation reaction [ ]
by the titration of an acid with an alkali [ ]

(d) A mixture of ammonium sulfate and sodium hydroxide was warmed in a test-tube. A gas was given off which turned red litmus paper blue.
State the name of this gas.
......................................................................................................

(e) Fertilisers containing ammonium salts are often slightly acidic.
(i) State the name of a compound which farmers add to the soil to make it less acidic.
......................................................................................................
(ii) Explain why it is important for farmers to control the acidity of the soil.
........................................................................................................................
........................................................................................................................

(f) The formula of ammonium sulfate is $(NH_4)_2SO_4$.
In this formula state:
(i) the number of different types of atoms present, ...................................
(ii) the total number of atoms present. ...................................

Many metals are extracted from their ores by reduction with carbon.
(a) Name the main ore of iron.
....................................................................................................................................... [1]
(b) Iron is extracted from its ore in a blast furnace.
(i) Other than iron ore, state the names of two other raw materials used in the extraction of iron.
1. ..........................................................
2. .......................................................... [2]
(ii) One of the reactions taking place in the blast furnace is
$$ \text{FeO + C } \rightarrow \text{ Fe + CO} $$
Write a word equation for this reaction.
....................................................................................................................................... [2]
(iii) The diagram shows a blast furnace. Label the diagram to show each of the following:
• the slag,
• where the molten iron collects,
• where air is blown into the furnace,
• where the iron ore is put into the furnace.
[Image]
[4]

(c) Zinc is extracted from an ore containing zinc sulfide.
Part of a zinc sulfide structure is shown below.
[Image]
Suggest the simplest formula for zinc sulfide.
....................................................................................................................................... [1]

Petroleum is a mixture of hydrocarbons.
Two of the processes carried out in an oil refinery are fractional distillation of petroleum and cracking of hydrocarbon fractions.

(a) Which property of hydrocarbons is used to separate petroleum into fractions?
Tick one box.

boiling point []
chemical reactivity []
electrical conductivity []
melting point []
[1]

(b) Match the fractions on the left with their uses on the right.
The first one has been done for you.



[4]

(c) Cracking is used to break down long chained alkanes into shorter chained alkanes and alkenes.

(i) State two conditions needed for cracking.
1. ............................................................................................................................................
2. ............................................................................................................................................ [2]

(ii) The hydrocarbon, $C_{14}H_{30}$, can be cracked to make ethene and one other hydrocarbon.
Complete the equation for this reaction.
$C_{14}H_{30} \rightarrow C_{2}H_{4} +$ .............
[1]

(iii) Draw the full structure of ethene showing all atoms and bonds.
[1]

(d) State the name of the polymer formed from ethene.
............................................................................................................................................
[1]

(e) Ethene is used to make ethanol.

(i) Which substance is needed for this reaction?
Put a ring around the correct answer.
ammonia hydrogen oxygen steam
[1]

(ii) Phosphoric acid is a catalyst in this reaction.
What do you understand by the term catalyst?
............................................................................................................................................
............................................................................................................................................
[1]

Some substances conduct electricity, others do not.

(a) Which three of the following conduct electricity? Tick three boxes.

aqueous sodium chloride □
ceramics □
copper □
graphite □
sodium chloride crystals □
sulfur □

[3]

(b) State the name given to a substance, such as plastic, which does not conduct electricity.

..........................................................................................................................

[1]

(c) Molten zinc chloride was electrolysed using the apparatus shown below.



(i) Choose a word from the list below which describes the positive electrode.
Put a ring around the correct answer.

anion anode cathode cation

[1]

(ii) State the name of the product formed during this electrolysis at

the negative electrode, ............................................................................................
the positive electrode. ..........................................................................................

[2]

(iii) Suggest the name of a non-metal which can be used for the electrodes in this electrolysis.

..........................................................................................................................

[1]