Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2012 Winter Zone 3

Part of the Periodic Table of elements is shown below.


(a) Answer the following questions using only the elements shown in the table above.
Write the symbol for an element which
(i) is used to fill light bulbs, ................................................................. [1]
(ii) is in Group VI and Period 3 of the Periodic Table, ................................................................. [1]
(iii) is a greyish-black solid, ................................................................. [1]
(iv) forms about 79\% of the air, ................................................................. [1]
(v) consists of single atoms with a full outer shell of electrons, ................................................................. [1]
(vi) is liberated at the cathode when concentrated hydrochloric acid is electrolysed. ................................................................. [1]

(b) Hydrogen reacts with chlorine to form hydrogen chloride.
(i) Complete the equation for this reaction.
$$H_2 + ext{..........} ightarrow ext{......HCl}$$ [2]
(ii) Draw the electronic structure of a chlorine molecule. Show only the outer shell electrons. [2]

Vinegar contains ethanoic acid. The formula of ethanoic acid is shown below.

(a) (i) On the formula above, put a ring around the carboxylic acid functional group. [1]
(ii) Write the simplest formula for a molecule of ethanoic acid. [1]

(b) Ethanoic acid reacts with sodium hydroxide to form the salt sodium ethanoate.
ethanoic acid + sodium hydroxide → sodium ethanoate + water
What type of chemical reaction is this?
........................................... [1]

(c) Sodium ethanoate is soluble in water. What do you understand by the term soluble?
........................................... [1]

(d) Which one of the following is the most likely pH value of ethanoic acid?
Put a ring around the correct answer.
pH 3 pH 7 pH 9 pH 13 [1]

(e) All acids react with carbonates. Complete the general equation for this reaction.
acid + carbonate → salt + .................. + ..................
.................. [2]

(f) The structure of sodium carbonate is shown below.

Write the simplest formula for sodium carbonate.
........................................... [1]

A student used the apparatus shown below to separate a mixture of coloured dyes. The solvent is not shown.

(a) On the diagram above, draw and label the position of the solvent at the start of the experiment. [1]
(b) The student let the solvent move up the filter paper to separate the dyes.
(i) State the name of this method of separation.
................................................................................................................. [1]
(ii) The student found that four different dyes had been separated by this method. On the diagram below draw
• the position of four separated dyes (show as spots)
• the solvent front (show as a line).

[3]
(c) Part of the structure of a dye called indigo is shown below.

Is this a saturated or unsaturated compound?
Give a reason for your answer.
................................................................................................................. [1]

Hydrogen can be manufactured by heating methane with steam.

$CH_4 + H_2O \xrightarrow{400^{\circ}C + \text{catalyst}} CO + 3H_2$

(a) (i) Draw the structure of methane showing all atoms and bonds. [1]

(ii) Methane is a greenhouse gas. What do you understand by the term greenhouse gas? [1]

(iii) State one source of the methane in the atmosphere. [1]

(iv) When 16 g of methane reacts completely with an excess of steam, 6 g of hydrogen are produced. Calculate the mass of methane required to produce 300 g of hydrogen.
Answer = .......................................... [1]

(b) More hydrogen can be formed by reacting the carbon monoxide with more steam at $500^{\circ}C$.

$CO + H_2O \rightleftharpoons CO_2 + H_2$

This reaction is reversible.
(i) How do you know from this equation that the reaction is reversible? [1]

(ii) What do you understand by the term reversible reaction? [1]

(iii) Carbon monoxide is a common atmospheric pollutant. State a source of the carbon monoxide in the atmosphere other than from the manufacture of hydrogen. [1]

(iv) Carbon dioxide is a product of the reaction between carbon monoxide and steam. Is carbon dioxide an acidic or a basic oxide? Give a reason for your answer. [1]

Ethanol can be made by

• an addition reaction with ethene or
• by fermentation.

Lead and lead compounds are common pollutants of the air.
(a) (i) State one source of lead in the air.
............................................................................................................. [1]
(ii) State one effect of lead on human health.
............................................................................................................. [1]
(b) Lead(II) oxide can be reduced by heating with carbon.
$$ \text{heat} $$
$$ \text{PbO + C} \rightarrow \text{Pb + CO} $$
(i) Write a word equation for this reaction.
............................................................................................................. [1]
(ii) Explain how you know that lead(II) oxide is reduced in this reaction.
.............................................................................................................
............................................................................................................. [1]
(iii) Explain why this reaction is described as endothermic.
............................................................................................................. [1]
(c) Lead nitrate solution reacts with sodium iodide solution.
$$ \text{lead nitrate + sodium iodide} \rightarrow \text{lead iodide + sodium nitrate} $$
Lead iodide is insoluble in water but the reactants and sodium nitrate are soluble.
Draw a labelled diagram to explain how you can separate lead iodide from the rest of the reaction mixture. [2]
(d) Complete the table below to show the number of protons, electrons and neutrons in the isotope of lead \(^{204}_{82}\text{Pb}\).
\( \begin{array}{|c|c|} \hline \text{number of protons} & \\ \hline \text{number of electrons} & \\ \hline \text{number of neutrons} & \\ \hline \end{array} \) [2]

The diagram below shows the apparatus used to electroplate a spoon with silver.

(a) Which is the anode? Put a ring around the correct answer in the list below.

aqueous silver nitrate
battery
iron spoon
rod of pure silver
[1]
(b) Describe what happens to the silver rod and the iron spoon during electroplating.
silver rod ..........................................................................................................................
iron spoon ...........................................................................................................................[2]
(c) Why are metal objects electroplated?
..........................................................................................................................[1]
(d) During the electroplating, silver atoms are converted to silver ions. Which one of the following statements about this reaction is correct? Tick one box.
Silver atoms gain electrons. ☐
Silver atoms lose neutrons. ☐
Silver atoms lose electrons. ☐
Silver atoms gain protons. ☐
[1]
(e) A student is given a slightly alkaline solution which contains chloride ions. Describe how the student could use aqueous silver nitrate to show that chloride ions are present in the solution.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................[3]
(f) Silver is a shiny metallic solid with a high melting point and boiling point. Describe two other physical properties of silver.
1 ..........................................................................................................................
2 ..........................................................................................................................[2]

The diagram shows a type of blast furnace built about 230 years ago. It was used to extract iron from iron ore.

(a) Which letter on the diagram shows
(i) where the solid raw materials are put into the furnace, ....................................... [1]
(ii) where air is blown into the furnace, ........................................................ [1]
(iii) where iron is removed from the furnace? ........................................................ [1]

(b) Describe the main reactions occurring in a blast furnace for extracting iron from iron ore. In your answer, include
● the names of the raw materials used
● the main chemical reactions which occur
● relevant word equations.
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
.............................................................................................................................................. [5]

(c) Iron reacts with hydrochloric acid.
(i) Complete the word equation for this reaction.
iron + hydrochloric acid $ ightarrow$ ....................... + .......................
....................... [2]

(ii) Iron(II) ions are formed in this reaction. Describe a test for iron(II) ions.
test ............................................................................................................................
result .......................................................................................................................... [2]

(d) Steel is an alloy of iron. Which one of the following statements about steel is correct? Tick one box.
○ Steel is a mixture of iron with sulfur atoms.
○ Stainless steel is commonly used to make car bodies.
○ The physical properties of steel are exactly the same as those of iron.
○ Steel is made by blowing oxygen through the molten iron obtained from the blast furnace. [1]