Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2016 Winter Zone 3

(a) Complete the table.

[Table_1]

particle | charge | relative mass
proton | +1 |
neutron | | 1
electron | |

[2]

(b) The following are isotopes of carbon.

$\begin{align} ^{12}_{6}\text{C} \quad ^{13}_{6}\text{C} \quad ^{14}_{6}\text{C} \end{align}$

(i) In terms of numbers of protons, neutrons and electrons, how are these three isotopes the same and how are they different?

They are the same because ...................................................................................................
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They are different because .............................................................................................
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[3]

(ii) Why do all isotopes of carbon have the same chemical properties?
.........................................................................................................................................
[1]

(c) Name two forms of the element carbon which have giant covalent structures.
.............................................................. and ..............................................................
[1]

(d) Complete the diagram to show the electron arrangement in a carbon dioxide molecule. Show the outer shell electrons only.



[2]

Beryllium is a metallic element in Group II.
(a) Give the electronic structure of a beryllium atom. [1]
...............................................................................................................................................
(b) Give the formula of beryllium oxide. [1]
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(c) (i) Describe the bonding in a metallic element such as beryllium. Include a labelled diagram and any appropriate charges in your answer. [3]
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(ii) Explain why metallic elements, such as beryllium are good conductors of electricity. [1]
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(d) Beryllium hydroxide is amphoteric. Beryllium hydroxide reacts with acids. The salts formed contain positive beryllium ions.
(i) Give the formula of the positive beryllium ion. [1]
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(ii) Write a chemical equation for the reaction between beryllium hydroxide and hydrochloric acid. [2]
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(iii) Beryllium hydroxide also reacts with alkalis. The salts formed contain beryllate ions, $\text{BeO}_2^{2-}$. Suggest a chemical equation for the reaction between beryllium hydroxide and sodium hydroxide solution. [2]
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When lead(II) nitrate is heated, two gases are given off and solid lead(II) oxide remains. The equation for the reaction is shown.
$$2\text{Pb(NO}_3\text{)}_2(s) \rightarrow 2\text{PbO}(s) + 4\text{NO}_2(g) + \text{O}_2(g)$$
(a) Calculate the $M_r$ of lead(II) nitrate.
.................................................................................................................. [1]

(b) 6.62 g of lead(II) nitrate are heated until there is no further change in mass.
(i) Calculate the mass of lead(II) oxide produced.
............................... g [2]
(ii) Calculate the volume of oxygen, $O_2$, produced at room temperature and pressure (r.t.p.).
............................... dm$^3$ [2]

(c) Describe a test for oxygen.
test ...................................................................................................................
result ................................................................................................................ [2]

(d) Lead(II) oxide is insoluble. A student adds solid lead(II) oxide to dilute nitric acid until the lead(II) oxide is in excess. Aqueous lead(II) nitrate and water are produced.
(i) What is meant by the term excess?
.................................................................................................................. [1]
(ii) How would the student know when the lead(II) oxide is in excess?
.................................................................................................................. [1]
(iii) Write a chemical equation for the reaction.
.................................................................................................................. [1]

Silicon(IV) oxide and sodium chloride have different types of bonding and structure.
(a) Name the type of bonding present in
silicon(IV) oxide, .......................................................................................................................
sodium chloride. ........................................................................................................................ [2]
(b) Name the type of structure present in silicon(IV) oxide.
.................................................................................................................................................. [1]
(c) (i) Silicon(IV) oxide has a high melting point. Explain why.
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.................................................................................................................................................. [2]
(ii) Silicon(IV) oxide is a poor conductor of electricity. Explain why.
.................................................................................................................................................. [1]
(d) Solid sodium chloride does not conduct electricity. However, it conducts electricity when molten.
Explain why solid sodium chloride does not conduct electricity, whereas molten sodium chloride does conduct electricity.
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(e) A concentrated aqueous solution of sodium chloride is electrolysed using carbon electrodes.
(i) Name the products formed at the electrodes.
product at the positive electrode (anode) ..............................................................
product at the negative electrode (cathode) ......................................................... [2]
(ii) Write an ionic half-equation for the reaction occurring at the negative electrode.
.................................................................................................................................................. [1]
(f) A dilute aqueous solution of sodium chloride is electrolysed using carbon electrodes.
Name the main product formed at the positive electrode.
.................................................................................................................................................. [1]
(g) Molten sodium chloride is electrolysed using carbon electrodes.
(i) Name the product formed at the negative electrode.
.................................................................................................................................................. [1]
(ii) Write an ionic half-equation for the reaction occurring at the negative electrode.
.................................................................................................................................................. [1]
(iii) Chlorine is produced at the positive electrode.
Give the test for chlorine.
test ..............................................................................................................................................
result .......................................................................................................................................... [2]

stage 1
(a) (i) Describe how sulfur is converted into sulfur dioxide.
................................................................................................................................. [1]
(ii) Write a chemical equation for the conversion of sulfur into sulfur dioxide.
................................................................................................................................. [1]

stage 2
(b) Sulfur dioxide is converted into sulfur trioxide according to the following equation.

$$2SO_2 + O_2 \rightleftharpoons 2SO_3$$
The reaction is carried out at a temperature of 450°C and a pressure of 1–2 atmospheres using a catalyst. The energy change, $\Delta H$, for the reaction is –196 kJ/mol.
(i) What is the meaning of the symbol $\rightleftharpoons$?
................................................................................................................................. [1]
(ii) Name the catalyst used in this reaction.
................................................................................................................................. [1]
(iii) Why is a catalyst used?
................................................................................................................................. [1]
(iv) If a temperature higher than 450°C were used, what would happen to the amount of sulfur trioxide produced? Give a reason for your answer.
................................................................................................................................. [2]
(v) Suggest a reason why a temperature lower than 450°C is not used.
................................................................................................................................. [1]
(vi) If a pressure higher than 1–2 atmospheres were used, what would happen to the amount of sulfur trioxide produced? Give a reason for your answer.
................................................................................................................................. [2]

stage 3
(c) (i) What is added to sulfur trioxide to convert it into oleum?
................................................................................................................................. [1]
(ii) Write a chemical equation for the conversion of sulfur trioxide into oleum.
................................................................................................................................. [1]

stage 4
(d) (i) What is added to oleum to convert it into sulfuric acid?
................................................................................................................................. [1]
(ii) Write a chemical equation for the conversion of oleum into sulfuric acid.
................................................................................................................................. [1]
(e) Give one use of sulfuric acid.
................................................................................................................................. [1]
(f) Sulfuric acid reacts with a hydrocarbon called benzene to produce benzenesulfonic acid, $C_6H_5SO_3H$. Benzenesulfonic acid is a strong acid which ionises to produce hydrogen ions, $H^+$, and benzenesulfonate ions, $C_6H_5SO_3^-$.
(i) What is meant by the term strong acid?
................................................................................................................................. [1]
(ii) Describe how to show that a 1 mol/dm³ solution of benzenesulfonic acid is a strong acid.
................................................................................................................................. [2]
(iii) Write a chemical equation for the reaction between benzenesulfonic acid and sodium carbonate, $Na_2CO_3$.
................................................................................................................................. [2]

Synthetic polyamides are made by condensation polymerisation.

(a) (i) What is meant by the term condensation polymerisation?
..........................................................................................................................
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.......................................................................................................................... [3]

(ii) Name another type of polymerisation.
.......................................................................................................................... [1]

(b) One repeat unit of a synthetic polyamide is represented by the following structure.



(i) Draw a ring around the amide link. [1]

(ii) Complete the diagrams to show the structures of the monomers used to produce the synthetic polyamide. Show all the missing atoms and bonds.




[2]

(iii) Name an example of a synthetic polyamide.
.......................................................................................................................... [1]

(c) Proteins and synthetic polyamides have similarities and differences.

(i) Name the type of compounds that are the monomers used to make up proteins.
.......................................................................................................................... [1]

(ii) Starting with a sample of protein, describe how to produce, separate, detect and identify the monomers which make it up.

Your answer should include
• the name of the process used to break down the protein into its monomers,
• the name of the process used to separate the monomers,
• the method used to detect the monomers after they have been separated,
• the method used to identify the monomers after they have been separated.
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