Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2017 Summer Zone 1

This question is about subatomic particles.
(a) Define the terms
proton number, ........................................................................................................................
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nucleon number. ........................................................................................................................
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(b) Why is the $^1\text{H}$ hydrogen atom the only atom to have an identical proton number and nucleon number?
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(c) Complete the table to show the number of protons, neutrons and electrons in the atoms and ions given.
[Table showing the number of protons, neutrons, and electrons]
| | number of protons | number of neutrons | number of electrons |
|----------------|------------------|-------------------|---------------------|
| $^{19}\text{F}$ | | | 9 |
| $^{26}\text{Mg}$ | 12 | | |
| $^{31}\text{P}^{3-}$ | | | |
| $^{87}\text{Sr}^{2+}$ | | | |
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(d) (i) Write the formula of the compound formed from fluorine and magnesium.
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(ii) Write the formula of the compound formed from Sr$^{2+}$ and P$^{3-}$.
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Some oxides of some elements are listed.
CO, CO₂, Na₂O, MgO, Al₂O₃
SiO₂, P₄O₁₀, SO₂, Cl₂O₇, Cr₂O₃
(a) Answer the following questions using only oxides from the list. Each oxide may be used once, more than once or not at all.
Give the formula of an oxide
(i) which is the main cause of acid rain, .........................................................................................................
(ii) which would give a solution of pH 14 when added to water, .........................................................................
(iii) which is coloured, ...................................................................................................................................
(iv) which is the major impurity in iron ore, ....................................................................................................
(v) which is amphoteric, ..................................................................................................................................
(vi) which is neutral. ......................................................................................................................................... [6]
(b) Amphoteric oxides and neutral oxides are different from each other.
(i) What is meant by the term amphoteric oxide?
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(ii) What is meant by the term neutral oxide?
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(a) A student prepared magnesium sulfate crystals starting from magnesium carbonate. The student carried out the experiment in four steps.

step 1 The student added excess magnesium carbonate to a small volume of dilute sulfuric acid until no more magnesium carbonate would react.

step 2 The student filtered the mixture.

step 3 The student heated the filtrate obtained from step 2 until it was saturated.

step 4 The student allowed the hot filtrate to cool to room temperature and then removed the crystals which formed.

(i) How did the student know when the reaction had finished in step 1?
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(ii) Name the residue in step 2.
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(iii) A saturated solution forms in step 3.
What is a saturated solution?
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(iv) Explain why magnesium sulfate crystals form during step 4.
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(b) Magnesium sulfate crystals are hydrated. Another student heated some hydrated magnesium sulfate crystals in a crucible and obtained the following results.

mass of hydrated magnesium sulfate crystals = 4.92 g
mass of water removed = 2.52 g

(i) Calculate the number of moles of water removed.
moles of water = .......................... mol [1]

(ii) Calculate the number of moles of anhydrous magnesium sulfate remaining in the crucible. The $M_r$ of anhydrous magnesium sulfate is 120.
moles of anhydrous magnesium sulfate = .......................... mol [1]

(iii) Calculate the ratio of moles of anhydrous magnesium sulfate : moles of water. Give your answer as whole numbers.
ratio = .............. : .............. [1]

(iv) Suggest the formula of hydrated magnesium sulfate crystals.
formula of hydrated magnesium sulfate crystals = ................................. [2]

(c) Lead(II) sulfate, PbSO$_4$, is insoluble.

Describe how you would prepare a pure dry sample of lead(II) sulfate crystals starting from solutions of lead(II) nitrate and sodium sulfate. Include a series of key steps in your answer.
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(d) Write the ionic equation for the reaction which takes place between solutions of lead(II) nitrate and sodium sulfate. Include state symbols.
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Zinc is a very important metal.
(a) Zinc is extracted from its ore, zinc blende. Zinc blende contains zinc sulfide, ZnS.
Zinc sulfide is converted to zinc oxide in an industrial process.
(i) Describe how zinc sulfide is converted to zinc oxide in this industrial process.
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(ii) Write the chemical equation for this reaction.
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(b) Zinc oxide is then reduced in a furnace.
(i) Name the substance added to the furnace to reduce the zinc oxide.
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(ii) Describe how the pure zinc is removed from the furnace and collected.
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(c) When rods of zinc and copper are placed into dilute sulfuric acid as shown, electricity is generated.

(i) Write the ionic half-equation for the reaction occurring at the zinc rod.
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(ii) Write the ionic half-equation for the reaction occurring at the copper rod.
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(iii) The copper rod was replaced by an iron rod.
Suggest the change, if any, in the intensity of the light emitted from the bulb and give a reason for your answer.
change ............................................................................................................................................
reason ............................................................................................................................................
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(a) Name the two pieces of apparatus needed to take the measurements shown on the graph.
1 .............................................................................................................................
2 .............................................................................................................................


(b) On the axes below, sketch a graph to show how the rate of reaction changes as the reaction proceeds.
Assume the initial rate of reaction is represented by the point at X.


(c) The total volume of gas collected was 180 $cm^3$ at room temperature and pressure.
Calculate the mass, in grams, of barium carbonate used.
$$\text{BaCO}_3 + 2\text{HCl} \rightarrow \text{BaCl}_2 + \text{H}_2\text{O} + \text{CO}_2$$
mass of barium carbonate = ......................... g


(d) The original graph has been drawn again.
On the grid, draw the graph expected if the same mass of barium carbonate is added as large lumps instead of as a powder. All other conditions are the same as in the original experiment.
Explain why your graph is different from the original graph.

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(e) The original graph has been drawn again.
On the grid, draw the graph expected if the concentration of dilute hydrochloric acid is changed from 0.1 mol/dm³ to 0.2 mol/dm³. All other conditions are the same as in the original experiment.
Explain, in terms of particles, why your graph is different from the original graph.

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(f) The experiment is changed and the mass of powdered barium carbonate is doubled. All other conditions are the same as in the original experiment. The acid is still in excess.
Deduce the volume of gas formed at room temperature and pressure, in $cm^3$, in this experiment.
volume of gas = ......................... $cm^3$

The alkenes and alkanes are both examples of homologous series which are hydrocarbons.
(a) What is meant by the term hydrocarbon?
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(b) Give three characteristics of an homologous series.
1 .........................................................................................................................................................................
2 ........................................................................................................................................................................
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(c) Name and draw the structure of the second member of the alkene homologous series.
Show all of the atoms and all of the bonds.
name ..................................................................................................................................................................
structure
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(d) Alcohols can be made from alkenes.
Name the reagent and conditions needed to convert an alkene into an alcohol.
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(e) The alcohol butanol, CH$_3$CH$_2$CH$_2$CH$_2$OH, can be converted into a carboxylic acid with four carbon atoms.
(i) Name the carboxylic acid formed from butanol and draw its structure. Show all of the atoms and all of the bonds.
name ..........................................................................................................................................................
structure
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(ii) Ethanoic acid can be formed from ethanol by fermentation. It can also be formed by the addition of a suitable chemical reagent.
Name the reagent needed to convert ethanol into ethanoic acid.
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(iii) State the type of chemical change which occurs when ethanol is converted into ethanoic acid.
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(f) Describe how a student could prepare the ester methyl ethanoate in a school laboratory.
In your description give
• the names of the two starting organic chemicals,
• the essential reaction conditions needed,
• a chemical equation for the reaction.
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