CIE iGCSE Co-Ordinated Science C2.4 Ions and ionic bonds Exam Style Questions Paper 3
Question
(a) Potassium is an element in the Periodic Table. (Topic: C8)
Use numbers from the list to complete the sentences about potassium.
Each number may be used once, more than once, or not at all.
1 2 3 8 19 20 39
(i) Potassium is an element in group … of the Periodic Table. (Sub-topic: C8.1)
▶️Answer/Explanation
Potassium is an element in Group 1 of the Periodic Table because it is an alkali metal.
(ii) A potassium atom has a total of … electrons. (Sub-topic: C8.1)
▶️Answer/Explanation
A potassium atom has a total of 19 electrons because its atomic number is 19.
(iii) A potassium ion has a positive charge of …. (Sub-topic: C8.2)
▶️Answer/Explanation
A potassium ion has a positive charge of 1 because it loses one electron to form K⁺.
(b) Sodium and chlorine react to form sodium chloride. (Topic: C8)
Fig. 8.1 shows the electronic structure of a sodium atom and a chlorine atom.
(i) Complete the diagrams in Fig. 8.2 to show the electronic structure of the ions in sodium chloride. (Sub-topic: C8.2)
▶️Answer/Explanation
Sodium ion (Na⁺): 2,8 (lost one electron)
Chloride ion (Cl⁻): 2,8,8 (gained one electron)
This transfer of electrons forms an ionic bond.
(c) Fig. 8.3 shows the electrolysis of concentrated aqueous sodium chloride. (Topic: C4)
(i) Complete Fig. 8.3 by labelling the: (Sub-topic: C4.2)
- Anode
- Cathode
- Electrolyte
▶️Answer/Explanation
Anode (Positive Electrode): Where oxidation occurs
Cathode (Negative Electrode): Where reduction occurs
Electrolyte: Concentrated aqueous sodium chloride (NaCl solution).
(ii) Hydrogen gas is one of the electrode products of this electrolysis. State the name of the other electrode product. (Sub-topic: C4.2)
▶️Answer/Explanation
The other electrode product is chlorine gas (Cl₂), which is released at the anode.
(iii) Describe the chemical test for hydrogen gas. State the observation for a positive result. (Sub-topic: C4.3)
▶️Answer/Explanation
Test: Hold a lighted splint near the gas.
Observation: If hydrogen gas is present, it will produce a ‘pop’ sound as it burns.
Question
(a) Sodium and chlorine are elements.
Sodium chloride is a compound.
Describe what is meant by an element and a compound.
element …………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………………………
compound …………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(b) Sodium reacts with chlorine to make sodium chloride.
Balance the symbol equation for this reaction.
………Na + Cl$_{2}$ ………NaCl
(c) When sodium reacts with chlorine, sodium atoms become sodium ions and chlorine atoms become chloride ions.
The electron configuration of a sodium atom is 2.8.1.
The electron configuration of a chlorine atom is 2.8.7.
State the electron configuration of a sodium ion and a chloride ion.
sodium ion ………………………………………..
chloride ion ………………………………………..
(d) Describe the difference in the solubility in water of an ionic compound compared with a covalent compound.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(e) Sodium chloride contains chloride ions.
Describe the test for chloride ions and state the observation for a positive result.
test …………………………………………………………………………………………………………………………..
observation ……………………………………………………………………………………………………………….
(f) Fig. 11.1 shows the electrolysis of concentrated aqueous sodium chloride.
Complete the sentences about the electrolysis of concentrated aqueous sodium chloride.
Electrolysis is defined as the breakdown of an ionic compound when
………………………………. or in aqueous solution by the passage of ……………………………….
The gas released at the negative electrode is ………………………………. and the gas
released at the positive electrode is ………………………………. .
▶️Answer/Explanation
Ans: 11(a) element – contains only one type of atom ;
compound – contains two or more elements (chemically combined) ;
11(b) 2Na + Cl$_{2}$ → 2NaCl ;
11(c) sodium ion 2.8 ;
chloride ion 2.8.8 ;
11(d) solubility of ionic compound is greater ;
11(e) add acidified aqueous silver nitrate ;
white precipitate ;
11(f) molten ;
electricity ;
hydrogen ;
chlorine ;