Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2017 Summer Zone 2

(a) State the name of the process that is used to
(i) separate oxygen from liquid air,
............................................................................................................................... [1]
(ii) separate the individual dyes in ink,
............................................................................................................................... [1]
(iii) produce ethanol from simple sugars,
............................................................................................................................... [1]
(iv) obtain water from aqueous sodium chloride,
............................................................................................................................... [1]
(v) separate the precipitate formed when aqueous silver nitrate is added to aqueous sodium chloride.
............................................................................................................................... [1]
(b) State what is meant by the terms
(i) element,
............................................................................................................................... [1]
...............................................................................................................................
(ii) compound,
............................................................................................................................... [1]
...............................................................................................................................
(iii) ion.
............................................................................................................................... [1]
...............................................................................................................................

Carbon and silicon are elements in Group IV of the Periodic Table. Both carbon and silicon exist as more than one isotope.
(a) Define the term isotopes.

(b) Complete the following table which gives information about carbon atoms and silicon atoms.

[Table with columns: carbon, silicon; and rows: proton number, electronic structure, nucleon number (12, 28), number of neutrons in one atom]

(c) Silicon has a giant structure which is similar to the structure of diamond.
(i) Name the type of bond which is present between silicon atoms in silicon. [1]

(ii) Suggest two physical properties of silicon. Use your knowledge of structure and bonding to explain why silicon has these physical properties. [4]
property 1 ........................................................................................................
reason 1 ........................................................................................................
property 2 ........................................................................................................
reason 2 ........................................................................................................

(d) Samples of air taken from industrial areas are found to contain small amounts of carbon monoxide.
(i) Explain how this carbon monoxide is formed. [2]

(ii) State why carbon monoxide should not be inhaled. [1]

(e) Carbon dioxide, $\text{CO}_2$, is a gas at room temperature and pressure, whereas silicon(IV) oxide, $\text{SiO}_2$, is a solid.
(i) Name the type of structure which the following compounds have. [2]
carbon dioxide ...........................................................................................[1]
silicon(IV) oxide ........................................................................................[1]
(ii) Use your knowledge of structure and bonding to explain why carbon dioxide is a gas at room temperature and pressure, whereas silicon(IV) oxide is a solid. [3]

(f) Silicon(IV) oxide is an acidic oxide. When silicon(IV) oxide reacts with alkalis, the salts formed contain the ion $\text{SiO}_3^{2-}$.
Write a chemical equation for the reaction between silicon(IV) oxide and aqueous sodium hydroxide. [2]

(a) Nitrogen in the air can be converted into ammonia by the Haber process. The chemical equation for the reaction is shown.

N₂ + 3H₂ ⇌ 2NH₃

(i) State the temperature and pressure used in the Haber process.

temperature .................................................

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

(a)(ii) Name the catalyst used in the Haber process.

..........................................................
[1]

(b) The ammonia produced in the Haber process can be oxidised to nitrogen(II) oxide at 900°C. The reaction is exothermic.

(i) Balance the chemical equation for this reaction.

4NH₃ + .....O₂ ⇌ .....NO + .....H₂O
[2]

(ii) Suggest a reason, other than cost, why a temperature greater than 900°C is not used.

..........................................................
[1]

(iii) Suggest a reason why a temperature less than 900°C is not used.

..........................................................
[1]

(c) Nitrogen(II) oxide can be reacted with oxygen and water to produce nitric acid as the only product. Write a chemical equation for this reaction.

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

(d) Describe how you would prepare a pure dry sample of copper(II) nitrate crystals in the laboratory using dilute nitric acid and solid copper(II) carbonate. Include a series of key steps in your answer. You should include a chemical equation for the reaction.

..........................................................

(a) Nickel and copper are transition elements.
State three chemical properties of transition elements.
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................ [3]

(b) Copper(II) oxide is a basic oxide but zinc oxide is an amphoteric oxide. Both oxides are insoluble in water.
You are provided with a mixture of solid copper(II) oxide and solid zinc oxide. Describe how you would obtain a sample of copper(II) oxide from this mixture.
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................ [3]

(c) Three cells are set up each using two metals.

(i) Write the ionic half-equation for the reaction occurring at the zinc electrode in cell 1.
................................................................................................................................................ [2]
(ii) Put the three metals, copper, nickel and zinc, in order of reactivity.
most reactive ...........................................................
↓
...........................................................
least reactive ........................................................... [1]
(iii) Complete the labelling in cell 3 by writing the polarity (+/−) of each electrode in the circles and calculating the reading on the voltmeter. [2]

(a) The elements in Group VII are known as the halogens. Some halogens react with aqueous solutions of halides.
(i) Complete the table by adding a \( \checkmark \) to indicate when a reaction occurs and a \( \times \) to indicate when no reaction occurs.

\[ \begin{array}{|c|c|c|c|} \hline & \text{aqueous potassium chloride} & \text{aqueous potassium bromide} & \text{aqueous potassium iodide} \\ \hline \text{chlorine} & \times & \checkmark & \\ \hline \text{bromine} & \times & & \times \\ \hline \text{iodine} & & & \times \\ \hline \end{array} \]
(ii) Write a chemical equation for the reaction between chlorine and aqueous potassium bromide.
\text{.................................................................................................................} [1]

(b) A sample of vanadium chloride was weighed and dissolved in water. An excess of aqueous silver nitrate, acidified with dilute nitric acid, was added. A precipitate of silver chloride was formed. The ionic equation for this reaction is shown.
\[ \text{Ag}^{+}(aq) + \text{Cl}^{-}(aq) \rightarrow \text{AgCl}(s) \]
The mass of silver chloride formed was 2.87 g.
(i) State the colour of the precipitate of silver chloride.
\text{.................................................................................................................} [1]
(ii) The relative formula mass of silver chloride, \text{AgCl}, is 143.5.
Calculate the number of moles in 2.87 g of \text{AgCl}.
\text{moles of AgCl } = \text{................................. mol} [1]
(iii) Use your answer to (b)(ii) and the ionic equation to deduce the number of moles of chloride ions, \text{Cl}^{-}, that produced 2.87 g of \text{AgCl}.
\text{moles of Cl}^{-} = \text{................................. mol} [1]
(iv) The amount of vanadium chloride in the sample was 0.01 moles.
Use this and your answer to (b)(iii) to deduce the whole number ratio of moles of vanadium chloride : moles of chloride ions.
Deduce the formula of vanadium chloride.
\text{moles of vanadium chloride : moles of chloride ions ..................... : .....................}
\text{formula of vanadium chloride ..........................................................} [2]

(c) Astatine is at the bottom of Group VII. Use your knowledge of the properties of the halogens to
(i) predict the physical state of astatine at room temperature and pressure,
\text{.................................................................................................................} [1]
(ii) write a chemical equation for the reaction between sodium and astatine.
\text{.................................................................................................................} [2]

(d) Iodine reacts with chlorine. The chemical equation is shown.
\[ \text{I}_2 + \text{Cl}_2 \rightarrow 2\text{ICl} \]
Use the bond energies to answer the questions.

\[ \begin{array}{|c|c|} \hline \text{bond} & \text{bond energy in kJ/mol} \\ \hline \text{I--I} & 151 \\ \hline \text{Cl--Cl} & 242 \\ \hline \text{I--Cl} & 208 \\ \hline \end{array} \]
(i) Calculate the total amount of energy required to break the bonds in 1 mole of \( \text{I}_2 \) and 1 mole of \( \text{Cl}_2 \).
\text{................................. kJ} [1]
(ii) Calculate the total amount of energy given out when the bonds in 2 moles of \( \text{ICl} \) are formed.
\text{................................. kJ} [1]
(iii) Use your answers to (d)(i) and (d)(ii) to calculate the overall energy change for the reaction.
\[ \text{I}_2 + \text{Cl}_2 \rightarrow 2\text{ICl} \]
\text{................................. kJ/mol} [1]

(a) An homologous series is a 'family' of organic compounds whose names have the same ending.
(i) Name the homologous series for which the names of the organic compounds end in -ene and -oic acid.
-ene ........................................................................................................................................................... [1]
-oic acid .................................................................................................................................................. [1]
(ii) State two characteristics of an homologous series.
................................................................................................................................................................
................................................................................................................................................................ [2]
(b) Propan-1-ol is a member of the homologous series of alcohols. It reacts in the same way as ethanol with acidified potassium manganate(VII) and with carboxylic acids.

Name the type of compound that is formed when propan-1-ol is heated with acidified potassium manganate(VII), ...............................................................................................
ethanoic acid and a suitable catalyst. ............................................................................................... [2]

(c) The structure of prop-2-enoic (acrylic) acid is shown.



(i) What would you see if prop-2-enoic acid were added to aqueous bromine, ....................................................................................................................
a solution of sodium carbonate. ................................................................................................. [2]
(ii) Prop-2-enoic acid can be polymerised to form poly(acrylic acid).
Suggest the type of polymerisation that occurs and draw one repeat unit of the polymer.
type of polymerisation ..............................................................................................................
repeat unit [3]