CIE iGCSE Co-Ordinated Science C3.1 Formulas Exam Style Questions Paper 3
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 ;
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.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(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.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(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 ;