Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2014 Winter Zone 2

(a) The electronic structure of five atoms, A, B, C, D and E, are shown below.

Answer the following questions about these structures.
Each structure can be used once, more than once or not at all.
Which structure:
(i) represents an atom of an element in Group V of the Periodic Table, ............................. $[1]$
(ii) has a complete outer shell of electrons, .......................................................................... $[1]$
(iii) represents an oxygen atom, ............................................................................................. $[1]$
(iv) has a proton number of 20, .............................................................................................. $[1]$
(v) is an atom of an element in Period 4 of the Periodic Table, ........................................... $[1]$
(vi) has a single valency electron? ............................................................................................ $[1]$

(b) Complete the following sentences about isotopes using words from the list below.
atoms        ions        molecules        neutrons        nuclei        protons
Isotopes are ............................. of the same element with the same number of ............................
but different numbers of ............................ . $[3]$

The table below shows some nutritional information on a bottle of apple juice.

[Table_1]

(a) Answer these questions using information from the table.

(i) Which negatively charged ion is present in the highest concentration? [1]

(ii) State the name of the ion, X, whose formula is $SO_4^{2-}$. [1]

(iii) The formulae for some chlorides are shown below.

aluminium chloride, $AlCl_3$
calcium chloride, $CaCl_2$
lead(IV) chloride, $PbCl_4$
potassium chloride, $KCl$

Deduce the formula for magnesium chloride. [1]

(iv) Calculate the mass of sugars in 250 cm$^3$ of this apple juice. [1]

(b) The fats in the apple juice are both saturated and unsaturated. Describe a test to distinguish between saturated and unsaturated compounds.

test ..........................................................................................................................
result with saturated compound .................................................................................
result with unsaturated compound ............................................................................ [3]

(c) Apple juice is slightly acidic.

(i) Which one of the following pH values is slightly acidic?

Put a ring around the correct answer.
pH 1    pH 5    pH 7    pH 9    pH 14 [1]

(ii) One of the acids found in apple juice is malic acid.
The structure of malic acid is shown below.



On the structure of malic acid above, put a ring around a carboxylic acid functional group. [1]

Hydrogen chloride gas can be prepared by the action of concentrated sulfuric acid on sodium chloride.
H$_2$SO$_4$ + 2NaCl $ ightarrow$ Na$_2$SO$_4$ + 2HCl
(a) Write the word equation for this reaction.
............................................................................................................................... [1]

(b) Hydrogen chloride dissolves in water to form hydrochloric acid.
(i) Complete the dot-and-cross diagram to show the arrangement of the outer shell electrons in water.
[2]
(ii) Describe what you would observe when a few drops of silver nitrate solution are added to hydrochloric acid.
............................................................................................................................... [2]

(c) The graph below shows how pH changes when aqueous ammonia is neutralised by hydrochloric acid.

(i) What is the pH of the aqueous ammonia at the start of the experiment?
............................................................................................................................... [1]
(ii) What volume of hydrochloric acid has been added when the pH is 10?
............................................................................................................................... [1]
(iii) What volume of hydrochloric acid has been added when the pH is changing most quickly?
............................................................................................................................... [1]

(d) Concentrated hydrochloric acid reduces manganese(IV) oxide, MnO$_2$, to manganese(II) chloride.
4HCl + MnO$_2$ $ ightarrow$ MnCl$_2$ + Cl$_2$ + 2H$_2$O
How does this equation show that manganese(IV) oxide gets reduced?
............................................................................................................................... [1]

(e) The table shows some properties of four metals, A, B, C and D, and their oxides.
[Table_1]
Which one of these metals is a transition metal? Use the information in the table to explain your answer.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]

Calcium carbonate reacts with dilute hydrochloric acid.
(a) Complete the symbol equation for this reaction.
$\text{CaCO}_3 + \text{......HCl} \rightarrow \text{CaCl}_2 + \text{CO}_2 + \text{............}$ [2]
(b) The rate of this reaction can be followed using the apparatus shown below.
(i) State the names of the pieces of apparatus labelled A and B.
A ...........................................................................................................................
B ............................................................................................................................ [2]
(ii) Explain why the mass of the reaction mixture decreases with time.
..................................................................................................................................... [1]
(c) The graph below shows how the mass of the reaction mixture changes with time. The calcium carbonate was in excess and large pieces of calcium carbonate were used.
(i) At what time was the reaction just complete?
............................................................................................................................ [1]
(ii) Calculate the total loss in mass of the reaction mixture in this experiment.
............................................................................................................................ [1]
(iii) How does the rate of reaction change when:
smaller pieces of calcium carbonate are used,
............................................................................................................................
the temperature is decreased,
............................................................................................................................
the concentration of hydrochloric acid is decreased?
............................................................................................................................ [3]
(d) When heated, calcium carbonate breaks down to form calcium oxide and carbon dioxide. Which two words from the list below describe this reaction? Tick two boxes.

• combustion
• decomposition
• endothermic
• exothermic
• oxidation

The structures of graphite and sodium chloride are shown below.

(a) Describe the similarity and differences in these structures.
.................................................................................................................................................
.................................................................................................................................................
.................................................................................................................................................
.................................................................................................................................................
.................................................................................................................................................
.................................................................................................................................................
................................................................................................................................................. [4]
(b) Graphite is a form of carbon. Carbon is an element.
(i) What is meant by the term element?
.................................................................................................................................................
................................................................................................................................................. [1]
(ii) Write a symbol equation for the complete combustion of carbon.
............................................................................................................... [2]

(c) The table shows some properties of four substances, A, B, C and D.
[Table_1]
| substance | melting point / ^\circ C | boiling point / ^\circ C | electrical conductivity |
|-----------|--------------------------|-------------------------|------------------------|
| A | -7 | +59 | does not conduct |
| B | -157 | -152 | does not conduct |
| C | +769 | +1930 | conducts when molten but not when solid |
| D | +1410 | +2355 | does not conduct |
Which one of these substances, A, B, C or D,
(i) is a liquid at room temperature, ................................................................. [1]
(ii) is a giant ionic structure, ................................................................. [1]
(iii) is a noble gas, ...................................................................... [1]
(iv) is a giant covalent structure? ................................................................. [1]

The table below shows some properties of the first five members of the alkane homologous series.

[Table_1]

(a) (i) What do you understand by the term homologous series?
.............................................................................................................................
............................................................................................................................. [2]

(ii) Deduce the molecular formula for pentane.
............................................................................................................................. [1]

(iii) Describe how the boiling points of these alkanes change as the number of carbon atoms increases.
............................................................................................................................. [1]

(iv) Deduce the density of liquid ethane.
............................................................................................................................. [1]

(b) Methane is a fuel which is a gas at room temperature. State the name of a fuel which is:
a solid at room temperature, ......................................................................................
a liquid at room temperature. ................................................................................. [2]

(c) The diagram below shows a distillation column used to separate petroleum into different fractions.



(i) On the diagram above:
• put a letter X to show where the temperature in the column is lowest,
• put a letter F to show where the fraction containing the largest molecules is collected,
• put a letter M to show where petroleum enters the distillation column. [3]

(ii) The refinery gas fraction contains ethane. Hydrogen is one of the products formed when ethane is cracked. Complete the symbol equation for the cracking of ethane.
$\text{C}_2\text{H}_6 \rightarrow \text{..................} + \text{..................}$ [2]

(iii) State the conditions needed for cracking.
............................................................................................................................. [2]

Gallium and aluminium are in Group III of the Periodic Table.
(a) The melting point of gallium is 30°C.
Use the kinetic particle theory to explain what happens when a spoon made of gallium is put into a cup of tea at 40°C.
In your answer, refer to:
● the change of state which occurs,
● the change in the arrangement of the particles,
● the change in the motion of the particles.
..............................................................................................................
..............................................................................................................
..............................................................................................................
..............................................................................................................
.............................................................................................................. [4]
(b) Gallium burns in air at a high temperature to form gallium(III) oxide.
Complete the symbol equation for this reaction.
......Ga + 3O$_2$ → ......Ga$_2$O$_3$ [2]
(c) Explain why aluminium is often used in containers for food and drinks.
..............................................................................................................
.............................................................................................................. [2]
(d) Aluminium chloride can be made by heating aluminium foil in a stream of chlorine.

(i) On the diagram above, draw an arrow to show where heat should be applied. [1]
(ii) At temperatures between 178°C and 400°C, aluminium chloride has the structure shown below.

Deduce the molecular formula of this structure.
.............................................................................................................. [1]
(iii) Some properties of aluminium and silver are shown in the table below.
[Table_1]
Use the information in the table to suggest why aluminium rather than silver is used in overhead power cables.
.............................................................................................................. [1]