Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2016 Winter Zone 3

The diagram shows part of the Periodic Table.

Answer the following questions using only the elements in the diagram.
Each element may be used once, more than once or not at all.
(a) Which element
(i) forms 21% of the air, ............................................................................................................................................... [1]
(ii) reacts with water to form a solution which turns litmus paper from red to blue, .............................................................................................................................. [1]
(iii) forms ions of type X$^{3+}$ which when tested with aqueous sodium hydroxide produce a green precipitate, .............................................................................................................................. [1]
(iv) is a red-brown liquid at room temperature and pressure, ............................................................................................................................................... [1]
(v) is a noble gas with only three complete electron shells? .............................................................................................................................. [1]

(b) The table gives some information about the properties of four metals.
[Table_1]
metal | density in g/cm$^3$ | relative strength | resistance to corrosion | relative electrical conductivity | melting point /$^{\circ}$C
chromium | 7.2 | 8 | very good | 8 | 1857
copper | 8.9 | 30 | good | 60 | 1283
iron | 7.9 | 21 | poor | 10 | 1535
titanium | 4.5 | 23 | very good | 2 | 1660
Which one of these metals is most suitable for making the frame of an aircraft?
Explain your answer using information from the table.
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A scientist analysed the substances present in a 1 dm^3 sample of river water in an agricultural area. The table shows the mass of each ion dissolved in the 1 dm^3 sample.
[Table_1]
(a) (i) Which negative ion has the highest concentration, in g/dm^3, in this sample of water?
...................................................................................................................................[1]
(ii) Give the name of the ion with the formula $SO_4^{2-}$.
...................................................................................................................................[1]
(iii) Calculate the mass of sodium ions in 1 dm^3 of this river water.
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(b) Describe a test for nitrate ions.
test .................................................................................................................................
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result ...............................................................................................................................
[3]

(c) The sample of river water also contains insoluble materials such as clay and the remains of dead animals and plants.
(i) What method could be used to separate insoluble materials from river water?
...................................................................................................................................[1]
(ii) Some of the remains of dead animals and plants contain food materials.
Which two of the following substances are constituents of food? Tick two boxes.

[1]
(iii) Particles of clay suspended in river water show Brownian motion.
Describe the movement of these particles.
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(d) Most of the nitrate ions in river water come from fertilisers.
(i) Explain why farmers use fertilisers.
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[2]
(ii) Ammonium nitrate is a fertiliser.
Ammonium nitrate reacts with calcium hydroxide.
ammonium nitrate + calcium hydroxide → calcium nitrate + ammonia + water
Explain why adding calcium hydroxide to the soil at the same time as nitrate fertilisers results in loss of nitrogen from the soil.
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[2]

Ethanol can be manufactured by fermentation and from ethene.
(a) Describe the manufacture of ethanol by fermentation and from ethene. In your answer include
• the essential conditions required for each reaction,
• one or more relevant word equations.
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(b) The table shows some properties of different alcohols.

| alcohol | formula | melting point/°C | boiling point/°C | relative viscosity |
|----------|---------|------------------|------------------|-------------------|
| methanol | CH₄O | –94 | 65 | 0.54 |
| ethanol | C₂H₆O | –117 | 79 | 1.08 |
| propanol | C₃H₈O | –126 | 98 | 1.94 |
| butanol | C₄H₁₀O | –89 | 117 | 2.54 |
| pentanol | C₅H₁₂O | –79 | ext{ }^{...} | 3.47 |

(i) Deduce the state of methanol at room temperature. Explain your answer.
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......................................................................................................................... [2]

(ii) Predict the boiling point of pentanol.
......................................................................................................................... [1]

(iii) Describe how the relative viscosity changes with the number of carbon atoms in the alcohol.
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(c) (i) Draw the structure of ethanol. Show all of the atoms and all of the bonds.
[2]

(ii) Give one major use of ethanol.
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(a) A crystal of blue dye was placed on top of some jelly. After 30 minutes some of the blue colour could be seen in the jelly. After 1 day the blue colour had spread out further into the jelly.

Use the kinetic particle model of matter to explain these observations.
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(b) The diagram shows the colour changes of the indicator bromocresol green at different pH values.

Predict the colour of bromocresol green
in pure water, ......................................................................................
in a strongly acidic solution. ......................................................................................

(c) The concentration of an alkali can be found by titrating it with an acid using the apparatus shown.

(i) State the names of the pieces of glassware labelled A and B.
A .................................................................................................................................
B .................................................................................................................................
(ii) Describe how you would carry out a titration using the apparatus shown.

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(a) (i) Is this reaction exothermic or endothermic? Explain your answer. ........................................................................................................................................... .......................................................................................................................................... [1]
(ii) The reaction is reversible. What information in the equation shows that this reaction is reversible? ........................................................................................................................................... [1]

(b) The diagram shows a furnace for making lime.

(i) On the diagram, write
- the letter C to show where the waste gases exit the furnace,
- the letter L to show where the lime is removed from the furnace. [2]
(ii) Suggest a reason for adding coke (carbon) to the furnace. .......................................................................................................................................... [1]

(c) Explain why farmers use lime to treat acidic soils. .......................................................................................................................................... .......................................................................................................................................... [2]

(d) Limestone is used to manufacture cement. The limestone is mixed with clay and heated to 1500°C. It is then mixed with calcium sulfate and crushed.
(i) Describe the test for sulfate ions.
test ........................................................................................................................................... result ......................................................................................................................................... [2]
(ii) Concrete is a mixture of cement, silicates and water. Part of the structure of a silicate is shown.

Deduce the formula for this silicate. .......................................................................................................................................... [1]

(e) Concrete contains small amounts of calcium oxide. This can react with rainwater to form calcium hydroxide.
(i) Calcium hydroxide is strongly alkaline. What is the most likely pH of a strongly alkaline solution? Draw a ring around the correct answer.
pH 2 pH 6 pH 7 pH 12 [1]
(ii) The calcium hydroxide on the surface of a piece of concrete reacts with carbon dioxide in the air. Complete the chemical equation for this reaction. $$ \text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{..............} $$ [1]
(iii) Limewater is an aqueous solution of calcium hydroxide. A teacher left an open beaker of limewater in the laboratory. After a week, the solution in the beaker was pH 7 and a white precipitate was observed.
Use the information in (e)(i) and (e)(ii) to help you explain these observations. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [3]

The Periodic Table is a method of classifying elements.
(a) (i) In what order are the elements arranged in the Periodic Table?
............................................................................................................................................. [1]
(ii) How does the character of the elements change from left to right across a period?
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(iii) Describe two trends in the properties of the elements going down Group I.
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(b) The halogens are a group of elements with diatomic molecules.
(i) Chlorine reacts with an aqueous solution of sodium iodide.
\[ \text{Cl}_2 + 2\text{NaI} \rightarrow \text{I}_2 + 2\text{NaCl} \]
What colour change would be observed in the solution?
from ........................................................ to ........................................................ [2]
(ii) Astatine, \text{At}_2, is a halogen.
Suggest why astatine does not react with aqueous potassium iodide.
............................................................................................................................................. [1]

(c) Chlorine reacts with hydrogen to form hydrogen chloride.
(i) Complete the chemical equation for this reaction.
\[ \text{Cl}_2 + ............... \rightarrow ......\text{HCl} \] [2]
(ii) Draw a diagram to show the electronic structure of a molecule of hydrogen chloride. Show only the outer shell electrons. [2]
(iii) Hydrochloric acid reacts with lithium hydroxide.
Complete the word equation for this reaction.

hydrochloric acid + lithium hydroxide \rightarrow .............................. [2]

The diagram shows the changes of state when phosphorus is cooled slowly to room temperature.

(a) Give the names of the changes of state labelled A and B.
A .................................................................................................................................
B .................................................................................................................................
[2]

(b) Describe the arrangement and motion of the particles in solid phosphorus.
arrangement ..........................................................................................................
motion ......................................................................................................................
[2]

(c) Is phosphorus(V) oxide an acidic oxide or basic oxide?
Explain your answer.
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[1]

(d) Phosphorus sulfide is a covalent molecule.

Predict two properties of phosphorus sulfide.
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[2]

(e) Many metal ores contain sulfides.
When zinc sulfide is heated in air the following reaction takes place.
zinc sulfide + oxygen → zinc oxide + sulfur dioxide
Explain why this reaction may be harmful to the environment.
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[2]