Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2021 Winter Zone 1

(a) A list of formulae is shown.

A\text{l}C\text{l}_3
CaCO_3
CO
CO_2
CoC\text{l}_2
CuSO_4
MgC\text{l}_2
\text{N}_2
NaC\text{l}
NH_3
\text{O}_2
SO_2

Answer the following questions using these formulae. Each formula may be used once, more than once or not at all.

State which formula represents:

(i) a compound that changes colour from white to blue when water is added
........................................................................................................................................ [1]

(ii) a compound that is used to make cement
........................................................................................................................................ [1]

(iii) an element that forms 78% of clean, dry air
........................................................................................................................................ [1]

(iv) a compound that contains an ion with a single positive charge
........................................................................................................................................ [1]

(v) a compound that dissolves in water to form an alkaline solution.
........................................................................................................................................ [1]

(b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of ammonia.

[2]

(c) State whether magnesium oxide is a basic oxide or an acidic oxide. Give a reason for your answer.
........................................................................................................................................
........................................................................................................................................ [1]

[Total: 8]

(a) Answer these questions using only the information in the table.

(i) State which of the positive ions has the highest concentration.
........................................................................................................................... [1]

(ii) Name the compound containing $\text{NH}_4^+$ and $\text{SO}_4^{2-}$ ions.
........................................................................................................................... [1]

(iii) Calculate the mass of magnesium ions in $400 \text{ cm}^3$ of rainwater.

mass = ....................................... mg [1]

(b) Describe a test for chloride ions.

test ..........................................................................................................................
observations ......................................................................................................... [2]

(c) Small amounts of carboxylic acids are also present in rainwater.
The structure of tartaric acid is shown.



(i) On the structure draw a circle around one alcohol functional group. [1]

(ii) Deduce the formula of tartaric acid to show the number of carbon, hydrogen and oxygen atoms.
........................................................................................................................... [1]

(d) Tartaric acid can be converted into compound A.
The formula of compound A is $\text{C}_3\text{H}_4\text{O}_3$.
Complete the table to calculate the relative molecular mass of compound A.

[Table_1]

relative molecular mass = ....................................... [2]

[Total: 9]

(a) Air is blown into the furnace.
State which letter on the diagram, B, C, D or E, shows where air is blown into the furnace.
[1]

(b) (i) Complete the chemical equation for the reduction of iron(III) oxide in the blast furnace.
$Fe_2O_3 + 3C \rightarrow ......Fe + ......CO$
[2]
(ii) Explain how this equation shows that iron(III) oxide is reduced.
[1]

(c) Calcium carbonate (limestone) is added to the blast furnace.
The calcium carbonate undergoes thermal decomposition.
(i) Complete the word equation for this reaction.

[2]
(ii) One of the products of this reaction reacts with impurities in the iron to form slag.
Use the information in the diagram to suggest how you know that molten slag is less dense than molten iron.
[1]

(d) (i) Use words from the list to complete these sentences about how steel is made from iron.
`acidic`, `basic`, `chlorides`, `methane`, `neutral`, `nitrogen`, `oxides`, `oxygen`, `sulfates`
A gas is blown through the molten iron. The name of this gas is ......................... .
Acidic gases are formed. These acidic gases react with ......................... ......................... .
[3]
(ii) State one use of mild steel.
[1]
(iii) Metals such as chromium are added to iron to make stainless steel.
The symbol for an isotope of chromium is shown.

Deduce the number of electrons, neutrons and protons in one atom of this isotope of chromium.
number of electrons .......................................................................................................
number of neutrons .....................................................................................................
number of protons ........................................................................................................
[3]

(e) Chromium conducts electricity and is shiny.
Give two other physical properties of chromium that are characteristic of all metals.
1 .................................................................................................................................
2 .................................................................................................................................
[2]

The table shows some properties of the Group I elements.

[Table_1]

(a) (i) Complete the table by predicting:
• the melting point of rubidium
• the density of lithium. [2]

(ii) Predict the observations when rubidium reacts with water.
.................................................................................................................................................
................................................................................................................................................. [1]

(b) Deduce the electronic structure of potassium. Use the Periodic Table to help you.
........................................................................................................................................................... [1]

(c) Lithium reacts with water to produce aqueous lithium hydroxide and a gas which ‘pops’ with a lighted splint.

(i) Name the gas which ‘pops’ with a lighted splint.
........................................................................................................................................................... [1]

(ii) Choose one pH value from the list that best describes the pH of aqueous lithium hydroxide.
Draw a circle around the correct answer.

pH 2 pH 5 pH 7 pH 13 [1]

(iii) Lithium reacts with nitrogen.
Complete the chemical equation for this reaction.
$$\text{......Li + N}_2 \rightarrow \text{......Li}_3\text{N}$$ [2]

[Total: 8]

The table shows the structures of some organic compounds.

[Table_1]

(a) Complete the table by naming the homologous series. The first one has been done for you. [2]

(b) Draw the structure of a compound containing two carbon atoms which belongs to the same homologous series as compound H. Show all of the atoms and all of the bonds. [1]

(c) State which compound in the table is an unsaturated hydrocarbon. Explain your answer. [1]

(d) State which compound in the table reacts with aqueous sodium hydroxide. Explain your answer. [1]

(e) State the names of the two compounds formed during the complete combustion of compound J. [2]

(f) Compound H can be polymerised.
(i) State the general name given to the small units which join together to form a polymer. [1]
(ii) Terylene is also a polymer. Give one use of Terylene. [1]

The diagram shows part of the structures of sodium bromide and graphite at room temperature and pressure.

(a) Describe the physical properties of these substances in terms of:
• volatility
sodium bromide ..........................................................................................................................
graphite .................................................................................................................................
• solubility in water
sodium bromide ..........................................................................................................................
graphite .................................................................................................................................
• electrical conductivity when solid.
sodium bromide ..........................................................................................................................
graphite ................................................................................................................................. [5]

(b) When dilute sulfuric acid is electrolysed using inert electrodes, oxygen gas is produced at the positive electrode.
Name the gas produced at the negative electrode.
................................................................................................................................. [1]

(c) Aqueous sodium bromide reacts with aqueous chlorine.
(i) Complete the word equation for this reaction.
[Table]
sodium bromide + chlorine $\rightarrow$ ................................ + ................................ [2]

(ii) Explain in terms of the reactivity of the halogens why aqueous sodium chloride does not react with aqueous bromine.
................................................................................................................................. [1]

This question is about nitrogen and compounds of nitrogen.

(a) When nitrogen is cooled to below −196°C it changes state from gas to liquid.

(i) Name the change of state from gas to liquid.
........................................................................................................................ [1]

(ii) Use the kinetic particle theory to describe the differences between nitrogen gas and liquid nitrogen in terms of:
⬤ the separation of the particles
........................................................................................................................
........................................................................................................................
........................................................................................................................
⬤ the motion of the particles.
........................................................................................................................
........................................................................................................................
........................................................................................................................ [4]

(b) Oxides of nitrogen are pollutants in the air.

(i) State one source of oxides of nitrogen in the air.
........................................................................................................................ [1]

(ii) Oxides of nitrogen contribute to acid rain.
Give one adverse effect of acid rain on buildings.
........................................................................................................................ [1]

(c) Nitric acid contains the nitrate ion.

(i) Use words from the list to complete the sentences to describe the test for nitrate ions.

aluminium ammonia chloride copper
hydroxide iron oxygen sulfate

Put the sample in a test-tube then add aqueous sodium ........................ .
Then add ........................ .
Warm gently. A gas is produced. The name of this gas is ........................ . [3]

(ii) Nitric acid reacts with calcium carbonate.
Complete the word equation for this reaction.



nitric acid + calcium carbonate → ........................ + ........................ + ........................ [3]

The rate of decomposition of aqueous hydrogen peroxide, $H_2O_2$, is increased by an enzyme.

$$2H_2O_2 \rightarrow 2H_2O + O_2$$

The rate of reaction is found by measuring the volume of oxygen gas given off as the reaction proceeds.

The results are shown on the graph.

(a) (i) Deduce the volume of oxygen gas released when the reaction is complete.   [1]

(ii) Deduce the volume of oxygen gas produced 50 seconds from the start of the reaction.  [1]

(b) The experiment was repeated using hydrogen peroxide of a higher concentration.

All other conditions stayed the same.

Draw a line on the grid to show how the volume of oxygen changes with time when hydrogen peroxide of a higher concentration is used. [2]

(c) Describe the effect each of the following has on the rate of decomposition of hydrogen peroxide.  [2]

• The reaction is carried out at a lower temperature.

All other conditions stay the same.

• The reaction is carried out without an enzyme.

All other conditions stay the same.

(d) Some metal oxides catalyse the decomposition of hydrogen peroxide.

The table shows the time taken to produce 20 cm³ of oxygen gas using three different metal oxide powders as catalysts.

All other conditions stay the same.

(i) Put the three oxides in order of their ability to catalyse the reaction. [1]

Put the best catalyst first.

(ii) The experiments with the metal oxide catalysts used powdered oxide.

Describe the effect on the rate of decomposition of hydrogen peroxide when large pieces of catalyst are used instead of powdered catalyst.

All other conditions stay the same.  [1]