Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2013 Winter Zone 3

(a) Choose from the list of metals below to answer the following questions.

aluminium
barium
calcium
iron
lithium
silver

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

(i) Which metal has an atom with three electrons in its outer electron shell?
.......................................................................................................... [1]

(ii) Which two metals are in the same Period of the Periodic Table?
.............................................. and .............................................. [1]

(iii) Which metal has an atom with three protons in its nucleus?
.......................................................................................................... [1]

(iv) Which metal has a nitrate which is used to test for halide ions?
.......................................................................................................... [1]

(v) Which metal is used in food containers because of its resistance to corrosion?
.......................................................................................................... [1]

(b) Describe two chemical properties of iron.
1. ..........................................................................................................
2. .......................................................................................................... [2]

(c) Describe briefly how iron from the blast furnace is made into steel.
..........................................................................................................
.......................................................................................................... [2]

Helium is in Group 0 of the Periodic Table.

(a) Describe the structure of a helium atom. Use your Periodic Table to help you. In your answer, include
• the type and number of subatomic particles present,
• the position of these particles in the atom,
• the relative charges on the particles.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.......................................................................................................................................... [5]

(b) Give one use of helium.
.......................................................................................................................................... [1]

(c) Some elements in Group 0 can form compounds with fluorine and oxygen. The structure of one of these compounds is shown below.



Calculate the relative molecular mass of this compound. Use your Periodic Table to help you. You must show all your working.

.......................................................................................................................... [2]

(d) Fluorine is a diatomic molecule. It melts at $-220^{\circ}\text{C}$ and boils at $-188^{\circ}\text{C}$.
(i) What is the physical state of fluorine
at room temperature, ..........................................................................................
at $-200^{\circ}\text{C}$? ..........................................................................................

.......................................................................................................................................... [2]

(ii) What is meant by the term $\textit{diatomic}$?
.......................................................................................................................................... [1]

This question is about calcium and some calcium compounds.

(a) Calcium is in Group II of the Periodic Table.
Complete the diagram below to show the electronic structure of calcium.

[2]

(b) Calcium reacts with hydrochloric acid to form a salt with the formula CaCl$_2$.
State the name of this salt.
...............................................................................................................................................
[1]

(c) Calcium carbonate reacts with hydrochloric acid.
The course of this reaction can be followed by measuring the volume of carbon dioxide given off at various time intervals.
The graph below shows the results obtained from an experiment using 0.15g of calcium carbonate in small pieces.


(i) What volume of gas is given off in the first 75 seconds of the reaction?
...............................................................................................................................................
[1]

(ii) On the grid opposite, sketch the line you would expect for the same reaction using large pieces of calcium carbonate. Assume that the mass of the calcium carbonate and all other conditions remain the same.
[2]

(iii) What would happen to the rate of this reaction if:
the temperature is increased,
...............................................................................................................................................
the concentration of hydrochloric acid is decreased?
...............................................................................................................................................
[2]

(d) When calcium carbonate is heated at high temperatures, calcium oxide and carbon dioxide are formed.

(i) Which one of the following words best describes this reaction?
Put a ring around the correct answer.
combustion decomposition exothermic reduction
[1]

(ii) Describe a test for carbon dioxide.
test ......................................................................................................................................
result .....................................................................................................................................
[2]

(e) Calcium oxide can be used to neutralise acidic industrial waste.

(i) Complete the word equation for the reaction of calcium oxide with nitric acid.
calcium oxide + nitric acid → ..................... + .....................
.....................
[2]

(ii) State one other use of calcium oxide.
...............................................................................................................................................
[1]

(iii) When calcium oxide reacts with water, heat is given off.
State the name given to a chemical reaction which gives off heat.
...............................................................................................................................................
[1]

The diagram shows how a liquid alkane can be cracked in a school laboratory to form a mixture of gaseous and liquid hydrocarbons.
(a) What piece of apparatus is missing from the diagram?
...................................................... [1]
(b) On the diagram above, put an X to show where the gas is collected. [1]
(c) What is the purpose of the catalyst?
...................................................... [1]
(d) Complete the equation to show the cracking of dodecane, $C_{12}H_{26}$, to form octane and one other substance.
$$C_{12}H_{26} \rightarrow C_{8}H_{18} + ext{..................}$$ [1]
(e) Cracking produces a mixture of shorter-chain alkanes and alkenes.
 (i) Describe what you would observe when a few drops of bromine water are added to an alkene.
...................................................... [1]
 (ii) Which one of the following compounds, A, B, C or D, is formed when bromine water reacts with ethene?

...................................................... [1]
 (iii) Poly(ethene) is made by combining ethene monomers. Which one of the following describes this reaction? Tick one box.
decomposition [ ]
neutralisation [ ]
oxidation [ ]
polymerisation [ ] [1]
(f) Many alkanes found in petrol are branched hydrocarbons. One example is shown below.

 (i) Write the molecular formula for this hydrocarbon.
...................................................... [1]
 (ii) What is meant by the term $hydrocarbon$?
...................................................... [1]
(g) State the name of the $two$ products formed when a hydrocarbon burns in excess air.
...................................................... and ...................................................... [2]

Ethanol can be made by fermentation.

(a) Apart from yeast, what other substances are present in the reaction mixture? Tick two boxes.
- copper sulfate
- ethene
- sugar
- methane
- water
[2]
(b) What method is used to separate ethanol from the rest of the reaction mixture?
.........................................................................................................................................
[1]
(c) Complete the structure of ethanol.

[1]
(d) Ethanol belongs to the alcohol homologous series. Which one of the following compounds also belongs to the alcohol homologous series? Put a ring around the correct answer.
- butene
- hexane
- ethanoic acid
- octanol
[1]
(e) Describe one other way, apart from fermentation, by which ethanol can be made on an industrial scale. Include the necessary reaction conditions in your answer.
.........................................................................................................................................
.........................................................................................................................................
.........................................................................................................................................
[3]

(a) When hydrated copper(II) sulfate is heated, the following reaction occurs:

$\text{CuSO}_4.5\text{H}_2\text{O}(s) \rightleftharpoons \text{CuSO}_4(s) + 5\text{H}_2\text{O}(l)$
hydrated copper(II) sulfate anhydrous copper(II) sulfate

(i) What does the sign $\rightleftharpoons$ mean?
.............................................................................................................................................................. [1]

(ii) Explain how this reaction is used as a chemical test for water.
..............................................................................................................................................................
.............................................................................................................................................................. [2]

(iii) Copper(II) sulfate is a salt.
Sodium chloride is also a salt. Solid sodium chloride does not conduct electricity.
Suggest \textbf{two} things you could do to make solid sodium chloride conduct electricity.
1. ......................................................................................................................................................
2. ...................................................................................................................................................... [2]

(b) Copper ore contains copper, iron and sulfur.
Copper is extracted by heating copper ore with sand and oxygen.

(i) In the first stage of this process, the copper ore is heated in a furnace.
A liquid mixture containing copper sulfide and iron sulfide is formed. The sand reacts with the impurities to form a slag.

[Image]

What information in the diagram above suggests that the slag is less dense than the mixture of copper and iron sulfides.
...................................................................................................................................................... [1]

(ii) In a later stage, copper sulfide is reacted with more oxygen.

$\text{Cu}_2\text{S} + \text{O}_2 \rightarrow 2\text{Cu} + \text{SO}_2$

How does this equation show that the sulfur in copper sulfide gets oxidised?
...................................................................................................................................................... [1]

(iii) Copper is purified by electrolysis using copper electrodes.

[Image]

Which letter, A, B, C or D, in the diagram above represents
the cathode, ................................................................................................................................
the electrolyte? ...................................................................................................................... [2]

The graph below shows how the temperature rises with time when a solid, P, is heated steadily and changes to a liquid and then to a gas.



(a) Use the information on the graph to deduce

the melting point of P, ...................................................
the state of P at 160°C. ........................................... [2]

(b) Explain what happens to the arrangement and motion of the particles when a solid changes to a liquid.

arrangement ..................................................
motion ....................................................... [2]

(c) A student placed a purple crystal in a flask of organic solvent. After 10 minutes, the crystal had completely disappeared and a dense purple colour was observed at the bottom of the flask. After 2 hours, the purple colour had spread throughout the solvent.



Use the kinetic particle theory to explain these observations. .................................................................. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ [3]

(a) State two differences between a mixture and a compound.
........................................................................................................... ........................................................................................................... ........................................................................................................... [2]
(b) Plant ash is a mixture of large insoluble particles and salts which are soluble in water. In parts of Africa, salts are traditionally obtained from plant ash. Water is added to the plant ash. The apparatus shown below is then used to remove the insoluble particles.

Explain how this apparatus separates the salts from the insoluble particles.
........................................................................................................... ........................................................................................................... ........................................................................................................... ........................................................................................................... [2]

(c) The composition and solubility of some salts found in the ash from the papyrus plant are shown in the table below.
[Table_1]
(i) Which salt in the table has the lowest solubility in g/dm^3?
........................................................................................................... [1]
(ii) Which negatively-charged ion is present in the highest amount in the ash?
........................................................................................................... [1]
(iii) Write the symbols for the two ions present in potassium sulfate.
........................................................................................................... [2]

(d) Sodium chloride reacts with lead(II) nitrate to form sodium nitrate and lead(II) chloride. Complete the symbol equation for this reaction. $$\text{.......NaCl + Pb(NO}_3\text{)}_2 \rightarrow \text{2NaNO}_3 \text{ + PbCl}_2$$ [1]

(e) Complete the following sentence about the formation of chloride ions. Chloride ions are formed when chlorine atoms gain ......................................... . [1]