Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2018 Winter Zone 1

The following formulae represent different substances.
$Al \quad Ag \quad CaCO_{3} \quad CH_{4} \quad Cl_{2} \quad Cu \quad SO_{2}$
Answer the following questions using only these substances.
Each substance may be used once, more than once or not at all.
State which substance is:
(a) used to make food containers ............................................... [1]
(b) added to a blast furnace to remove impurities during the production of iron ................. [1]
(c) the main constituent of natural gas ........................................ [1]
(d) a cause of acid rain ......................................................... [1]
(e) a gas which bleaches damp litmus paper ................................... [1]
(f) a gas which contributes to climate change. .................................. [1]

The table gives some information about four different particles, A, B, C and D.

[Table_1]

(a) Complete the table. The first row has been done for you. [4]
................................................................................................................................................

(b) Give two particles from the table which are isotopes of each other. [1]
................................................................................................................................................

(c) Element Z is in the same group of the Periodic Table as A and is less reactive than A.
State the identity of element Z. [1]
................................................................................................................................................

(d) C is unreactive.
Use information from the table to explain why. [1]
................................................................................................................................................

(a) Copper(II) nitrate decomposes when heated. Two gases, oxygen and nitrogen dioxide, and a solid are made in the reaction.
A sample of copper(II) nitrate was decomposed using the apparatus shown.

(i) Complete the chemical equation for the reaction.
$2\text{Cu(NO}_3\text{)}_2 \rightarrow \text{O}_2 + \quad\text{......NO}_2 + \text{.....................}$ [2]
(ii) Only oxygen gas is collected at X.
Explain why.
...............................................................................................................................
............................................................................................................................... [1]

(b) Nitrogen dioxide and other oxides of nitrogen are formed in car engines.
Explain how nitrogen dioxide is formed in car engines.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
...................................................................................................................................... [2]

(c) A teacher heated 18.8 g of copper(II) nitrate.
(i) Calculate the number of moles of copper(II) nitrate present in the 18.8 g.
.............................. mol [2]
(ii) Calculate the maximum number of moles of oxygen that can be made by heating 18.8 g of copper(II) nitrate.
.............................. mol [1]
(iii) Calculate the maximum volume of oxygen at room temperature and pressure, in cm$^3$, that can be made by heating 18.8 g of copper(II) nitrate.
.............................. cm$^3$ [1]

(d) A sample of copper(II) nitrate was dissolved in water to form an aqueous solution.
The aqueous solution was split into three portions. A separate test was done on each portion as shown.
[Table_1]
(i) Give the formula of the light blue precipitate formed in test 1.
...................................................................................................................... [1]
(ii) Explain the changes seen in test 2.
......................................................................................................................
......................................................................................................................
......................................................................................................................
...................................................................................................................... [3]
(iii) Identify the \textbf{two} reagents that must be added to the aqueous copper(II) nitrate in test 3.
1 .................................................................................................................
2 ................................................................................................................. [2]

(e) Copper(II) nitrate can be made by reacting copper(II) carbonate with nitric acid. One of the products is carbon dioxide.
(i) Write a chemical equation for the reaction of copper(II) carbonate with nitric acid.
...................................................................................................................... [2]
(ii) Carbon dioxide is added to the air by living things.
Name the chemical process by which living things add carbon dioxide to the air.
...................................................................................................................... [1]
(iii) Carbon dioxide is removed from the air by plants.
Name the chemical process by which plants remove carbon dioxide from the air.
...................................................................................................................... [1]

(a) Sulfuric acid is made industrially by a four-step process.

step 1 Sulfur is burned in air to produce sulfur dioxide.
step 2 Sulfur dioxide is converted into sulfur trioxide.
step 3 Sulfur trioxide is reacted with concentrated sulfuric acid to produce oleum.
step 4 Oleum is reacted with water to produce concentrated sulfuric acid.

(i) Some sulfur is obtained by mining.
Name one other major source of sulfur.
................................................................................................................................. [1]

(ii) What is the name of the process by which sulfuric acid is made industrially?
................................................................................................................................. [1]

(iii) Describe the conversion of sulfur dioxide into sulfur trioxide in step 2.
In your answer, include:
- a chemical equation for the reaction
- the essential reaction conditions.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
................................................................................................................................. [5]

(b) When concentrated sulfuric acid is added to glucose, $C_6H_{12}O_6$, a black solid is produced. The concentrated sulfuric acid acts as a dehydrating agent.

(i) What is removed from the glucose in this reaction?
................................................................................................................................. [1]

(ii) Name the black solid produced in this reaction.
................................................................................................................................. [1]

(c) The gas hydrogen sulfide, $H_2S$, is produced when concentrated sulfuric acid is added to solid potassium iodide.
The reaction involves oxidation.

(i) Define the term oxidation in terms of electron transfer.
................................................................................................................................. [1]

(ii) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of hydrogen sulfide. Show outer shell electrons only.
[2]

(iii) Hydrogen sulfide has a simple molecular structure.
Explain why hydrogen sulfide has a low boiling point.
.................................................................................................................................
.................................................................................................................................
................................................................................................................................. [2]

(d) Dilute sulfuric acid reacts with aqueous sodium hydrogencarbonate in a neutralisation reaction.

$H_2SO_4(aq) + 2NaHCO_3(aq) \rightarrow Na_2SO_4(aq) + 2H_2O(l) + 2CO_2(g)$

In a titration, 0.200 mol/dm³ aqueous sodium hydrogencarbonate was used to neutralise 20.0 cm³ of dilute sulfuric acid of concentration 0.150 mol/dm³.

(i) Calculate the number of moles of dilute sulfuric acid used in the titration.
.............................. mol [1]

(ii) Calculate the number of moles of sodium hydrogencarbonate needed to neutralise the dilute sulfuric acid.
.............................. mol [1]

(iii) Calculate the volume, in cm³, of 0.200 mol/dm³ aqueous sodium hydrogencarbonate needed to neutralise the dilute sulfuric acid.
.............................. cm³ [1]

Hydrogen gas reacts with iodine gas. The equation is shown.

\[ \text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g) \]
The reaction is reversible and can reach equilibrium.

(a) What is meant by the term equilibrium?
..........................................................
..........................................................
.......................................................... [2]

(b) The graphs show how pressure affects the yield of hydrogen iodide, HI, at two different temperatures.


(i) Explain why the yield at 500 °C does not change as the pressure is increased.
..................................................... [1]

(ii) What can you conclude from the difference in the yield of hydrogen iodide at the two temperatures shown? Explain your answer.
..................................................... [2]

(c) The graph shows how the concentration of hydrogen iodide, HI, changes after hydrogen gas and iodine gas are mixed together in a sealed container.


(i) When is the rate of reaction fastest?
..................................................... [1]

(ii) The reaction was repeated at the same temperature and pressure but in the presence of a catalyst.
Draw a graph on the same axes to show how the concentration of hydrogen iodide changes with time in the presence of a catalyst. [2]

(d) A mixture of hydrogen gas and iodine gas is allowed to reach equilibrium.

(i) Increasing the pressure of a gas increases its concentration.
State and explain the effect of increasing the pressure on the rate of the forward reaction.
..................................................... [2]

(ii) State and explain the effect of increasing the temperature on the rate of the reverse reaction.
..................................................... [3]

(a) Ethane, $C_2H_6$, is a member of the homologous series called alkanes.
Ethanol, $C_2H_5OH$, is a member of the homologous series called alcohols.
(i) Alkanes are hydrocarbons.
What is meant by the term hydrocarbon?
..........................................................................................................................................................................
.................................................................................................................................................................................................................................. [2]
(ii) All members of a homologous series can be represented by a general formula.
State the general formula of:
• alkanes .................................................................................................................................................................
• alcohols .................................................................................................................................................................
[2]
(iii) State two characteristics, other than having the same general formula, of members of a homologous series.
1 ............................................................................................................................................................................
..................................................................................................................................................................................
2 ................................................................................................................................................................................
................................................................................................................................................................................. [2]

(b) Ethane can react with chlorine in a substitution reaction.
(i) State one essential reaction condition.
.......................................................................................................................................................................... [1]
(ii) Draw the structure of the organic product formed by substitution of one of the hydrogen atoms in ethane with chlorine. Show all of the atoms and all of the bonds.
[1]
(iii) Name the product of the substitution reaction between ethane and chlorine that does not contain carbon.
.......................................................................................................................................................................... [1]

(c) Propan-1-ol is an alcohol.
The structure of propan-1-ol is shown.



Propan-1-ol reacts with ethanoic acid to form an ester.
Give the name of the ester formed in this reaction.
.......................................................................................................................................................................... [1]

(d) Ester Y has the structure shown.



(i) Give the molecular formula of ester Y.
.......................................................................................................................................................................... [1]
(ii) Draw the structures of the carboxylic acid and the alcohol used to make ester Y. Show all of the atoms and all of the bonds. Give the name of the carboxylic acid and the alcohol.
structure of the carboxylic acid
..........................................................................................................................................................................
name of the carboxylic acid .........................................................................................................................
structure of the alcohol
..........................................................................................................................................................................
name of the alcohol ......................................................................................................................................... [4]

(e) Nylon is a polyamide.
Complete the diagram to show the structure of nylon. Show all of the atoms and all of the bonds present in the linkages.



[3]