CIE iGCSE Co-Ordinated Science C8.3 Group VII properties Exam Style Questions Paper 3
Question
(a) Chlorine reacts with hydrogen to make hydrogen chloride.
(i) Construct the word equation for this reaction.
(ii) Hydrogen chloride gas is a covalent compound.
Explain why hydrogen chloride gas is a covalent compound and not an ionic compound.
(iii) Fig. 5.1 shows the electronic structure in atoms of hydrogen and chlorine.
Draw a dot-and-cross diagram to show the arrangement of outer-shell electrons in a molecule of hydrogen chloride gas.
(iv) Hydrogen chloride dissolves in water to make dilute hydrochloric acid.
The pH of the hydrochloric acid is found using a pH probe.
Describe one other way of finding the pH of dilute hydrochloric acid.
(v) Suggest the pH of the dilute hydrochloric acid.
(b) Table 5.1 shows information about three Group VII elements.
(i) Complete Table 5.1.
(ii) State the name given to Group VII of the Periodic Table.
(iii) Explain why chlorine, bromine and iodine are all in Group VII of the Periodic Table.
Use ideas about electrons in your answer.
▶️Answer/Explanation
Ans :
5(a)(i) hydrogen + chlorine → hydrogen chloride ;
5(a)(ii) two non-metals bonding ;
5(a)(iii) one pair of bonding electrons ;
all else correct ;
5(a)(iv) use universal indicator ;
colour indicates the pH ;
5(a)(v) any value between 1 and 3 ;
5(b)(i)
5(b)(ii) halogens ;
5(b)(iii) all have 7 electrons in their outer shell ;
Question
(a) Chlorine, bromine and iodine are halogens in Group VII of the Periodic Table.
Some of these statements about the halogens are correct and some are incorrect.
Place a tick (✓) in the boxes next to the correct statements.
(b) A chlorine atom has a nucleon number of 37 and has 17 electrons.
(i) Determine the number of protons and the number of neutrons in this chlorine atom.
number of protons = ………………………………………………………
number of neutrons = …………………………………………………….
(ii) State the part of the atom that contains the protons and neutrons.
…………………………………………………………………………………………………………………….
(c) Chlorine is made during the electrolysis of concentrated aqueous sodium chloride as shown below in Fig. 2.1.
(i) State the electrode at which chlorine forms during this process.
…………………………………………………………………………………………………………………….
(ii) State the other gaseous product of this electrolysis.
…………………………………………………………………………………………………………………….
(iii) Explain why graphite is used to make the electrodes.
…………………………………………………………………………………………………………………….
(iv) Explain why electrolysis is an example of a chemical change and not a physical change.
…………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(d) Explain why the drinking water supply for a town is treated with chlorine.
……………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans: 2(a)
;;
2 ticks 2 correct = 2 marks
3 ticks 2 correct = 1 mark
2 ticks 1 correct = 1 mark
1 tick 1 correct = 1 mark
4 ticks 2 correct = 0 marks
2(b)(i) protons = 17 ;
neutrons = 20 ;
2(b)(ii) nucleus ;
2(c)(i) anode / positive ;
2(c)(ii) hydrogen ;
2(c)(iii) it is inert / will not react / good electrical conductor ;
2(c)(iv) new substances formed / cannot be reversed ;
2(d) kills microbes / sterilise water ;
Question
(a) Table 5.1 shows some information about three Group VII elements.
Complete Table 5.1.
(b) State the name given to the Group VII elements in the Periodic Table.
……………………………………………………………………………………………………………………………
(c) An atom of one of the isotopes of iodine contains 53 protons and 74 neutrons.
Some statements about iodine are shown below.
Place a tick (√) to show the correct statements about iodine.
(d) Describe what is observed when aqueous silver nitrate is added to aqueous potassium chloride
and to aqueous potassium bromide.
aqueous potassium chloride ………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………
aqueous potassium bromide ……………………………………………………………………………………….
…………………………………………………………………………………………………………………………………
(e) A gas jar filled with air is placed on top of a gas jar filled with orange bromine vapour. After
several hours, the bromine vapour has mixed with the air.
This is shown in Fig. 5.1.
Explain why the bromine mixes with the air.
Use ideas about the movement of molecules in your answer.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
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▶️Answer/Explanation
Ans: 5(a)
one mark for each column ;;;
5(b) halogens ;
5(c) √
no tick / 
√
√
3 ticks and 3 correct = 2 marks
4 ticks and 3 correct = 1 mark
3 ticks and 2 correct = 1 mark
2 ticks and 2 correct = 1 mark
;;
5(d) potassium chloride – white precipitate ;
potassium bromide – cream/off white precipitate ;
5(e) diffusion ;
molecules move randomly from place to place / spread out / from high to low concentration ;
Question
(a) The list gives the names of seven elements.
aluminium carbon copper chlorine
helium phosphorus sulfur
State which of the elements in the list:
(i) forms diamond and graphite ……………………………………………………………………………
(ii) is a halogen …………………………………………………………………………………………………..
(iii) is electroplated onto another metal …………………………………………………………………..
(iv) is extracted from bauxite …………………………………………………………………………………
(v) is used in the manufacture of sulfuric acid …………………………………………………………
(vi) is used to sterilise drinking water ……………………………………………………………………..
(b) The formula of phosphorus oxide is P4O10.
State the number of atoms of phosphorus and of oxygen contained in one molecule of phosphorus oxide.
phosphorus ………………………………………………………………..
oxygen ………………………………………………………………………..
(c) Explain why phosphorus oxide makes an acidic solution when it dissolves in water.
(d) Phosphorus is contained in fertilisers.
State the two other elements commonly found in fertilisers.
1 …………………………………………………………………………
2 …………………………………………………………………………
▶️Answer/Explanation
Ans : 2(a)(i) carbon ;
2(a)(ii) chlorine ;
2(a)(iii) copper ;
2(a)(iv) aluminium ;
2(a)(v) sulfur ;
2(a)(vi) chlorine ;
2(b) phosphorus 4 oxygen 10 ;
2(c) non-metal oxides are acidic or non-metal oxides form acidic solutions ;
2(d) nitrogen ;
potassium ;
Question
(a) Orange bromine gas, Br$_{2}$, is put into the bottom of a gas jar which is immediately sealed.
After a short time, the bromine gas spreads out to fill the gas jar.
This process is called diffusion.
Fig. 11.1 shows the diffusion of bromine.
Describe the process of diffusion in terms of the movement of particles.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
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(b) Chlorine and bromine are both halogens.
State the name of one other element that is a halogen.
…………………………………………………………………………………………………………………………………
(c) Chlorine is in Period 3 of the Periodic Table.
Describe the change in metallic character across Period 3.
…………………………………………………………………………………………………………………………………
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(d) Explain why the drinking water for a city is treated with chlorine.
…………………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
(e) Complete the dot-and-cross diagram to show the bonding in a molecule of chlorine Cl$_{2}$.
Only show the outer shell electrons.
(f) Hydrogen and chlorine combine to make hydrogen chloride, HCl.
(i) Balance the symbol equation for this reaction.
H$_{2}$ + Cl$_{2}$→ …….. HCl
(ii) Explain why hydrogen chloride is a covalent compound and not an ionic compound.
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 11(a) gas particles in (constant) random motion ;
(particles move) from region of high concentration to region of low concentration ;
11(b) iodine / fluorine / astatine ;
11(c) metallic to non-metallic (from left to right) ;
11(d) to kill, microorganisms/bacteria/pathogens ;
11(e) shared pair ;
correct number of electrons on each atom / 14 electrons in total ;
11(f)(i) 2 HCl ;
11(f)(ii) two non-metals bonding / shared pair of electrons ;
Question
(a) Table 11.1 contains data for some elements in Group VII of the Periodic Table. (Sub-topic: C8.3)
| Element | Formula | Physical state at room temperature |
|---|---|---|
| Chlorine | Cl2 | |
| Bromine | Br2 | Liquid |
| Iodine | Solid |
(i) State the formula of iodine.
(ii) Explain why a chlorine molecule is described as diatomic.
(iii) Predict the physical state of chlorine.
(iv) State the name given to the elements in Group VII of the Periodic Table.
▶️Answer/Explanation
(i) The formula of iodine is I2.
(ii) A chlorine molecule is described as diatomic because it consists of two atoms bonded together.
(iii) The physical state of chlorine is gas.
(iv) The elements in Group VII of the Periodic Table are called halogens.
(b) Sub-topic: C8.3
(i) Explain why the drinking water supply for a large town is treated with chlorine.
(ii) Describe the chemical test for chlorine and give the positive result.
test ……………………………………………………………………………………………………………………
result …………………………………………………………………………………………………………………
▶️Answer/Explanation
(i) The drinking water supply is treated with chlorine to kill microorganisms/bacteria and make the water safe for consumption.
(ii) The chemical test for chlorine involves using damp litmus paper. The positive result is that the litmus paper is bleached (turns white).
(c) Hydrogen and chlorine combine to produce hydrogen chloride (HCl). (Sub-topic: C2.5)
(i) Balance the symbol equation for this reaction.
H2 + Cl2 → …… HCl
(ii) Complete the dot and cross diagram to show the bonding in a molecule of hydrogen chloride, HCl.
You only need to show the outer shell electrons.
(iii) State why hydrogen chloride is a covalent compound and not an ionic compound.
▶️Answer/Explanation
(i) The balanced symbol equation is:
H2 + Cl2 → 2HCl
(ii) The dot and cross diagram for HCl:
H (1 electron) + Cl (7 electrons) → H:Cl (shared pair of electrons).
(iii) Hydrogen chloride is a covalent compound because it is formed by the sharing of electrons between hydrogen and chlorine, which are both non-metals. Ionic compounds are formed by the transfer of electrons between metals and non-metals.
Question
(a) Table 2.1 shows information about three Group VII elements.
Table 2.1
| Element | Formula | Colour | Physical state at 20 °C |
|---|---|---|---|
| Chlorine | Cl2 | Gas | |
| Bromine | Orange | ||
| Iodine | I2 | Grey |
(i) Complete Table 2.1.
▶️Answer/Explanation
| Element | Formula | Colour | Physical state at 20 °C |
|---|---|---|---|
| Chlorine | Cl2 | Pale green | Gas |
| Bromine | Br2 | Orange | Liquid |
| Iodine | I2 | Grey | Solid |
(ii) State the name given to the Group VII elements in the Periodic Table.
▶️Answer/Explanation
Halogens
(b) Bromine reacts with hydrogen to make hydrogen bromide. Construct the word equation for this reaction.
▶️Answer/Explanation
Hydrogen + Bromine → Hydrogen bromide
(c) Aqueous bromine is orange. Predict the colour change, if any, when aqueous bromine is mixed with ethene gas. Explain your answer.
▶️Answer/Explanation
Colour change: Orange to colourless
Explanation: Ethene is an unsaturated hydrocarbon with a double bond, which reacts with bromine, causing the orange colour of bromine to disappear as it forms a colourless dibromoethane.
(d) An aqueous solution is tested to see if bromide ions are present. State the test for aqueous bromide ions and give the observation for a positive result.
▶️Answer/Explanation
Test: Add aqueous silver nitrate to the solution.
Observation: A cream-coloured precipitate forms.
(e) Fig. 2.1 shows the electrolysis of molten lead(II) bromide using inert electrodes.
Identify the substances formed at the cathode and the anode.
▶️Answer/Explanation
At cathode: Lead
At anode: Bromine