CIE iGCSE Co-Ordinated Science C7.1 The characteristic properties of acids and bases 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) Limestone is insoluble in water.
Limestone is mixed with water and poured through filter paper.
(i) Explain how filter paper separates limestone from water.
(ii) The filtrate is tested to find its pH number.
One way of finding the pH number is to use a pH meter.
Describe one other way to find the pH number of the filtrate.
(b) Limestone is sometimes added to soil to reduce soil acidity.
Limestone is mainly calcium carbonate which reacts with acid.
(i) This soil treatment adds carbon dioxide to the atmosphere.
State one other reason why the amount of carbon dioxide in the atmosphere is increasing.
(ii) Describe how an increase in carbon dioxide in the atmosphere affects the environment.
(c) A student investigates the rate of reaction between excess dilute hydrochloric acid and a piece of limestone.
Fig. 11.1 shows the apparatus used.
The student measures the volume of carbon dioxide in the measuring cylinder every 20 seconds for 280 seconds.
A graph of the student’s results is shown in Fig. 11.2.
(i) Use Fig. 11.2 to find the total volume of carbon dioxide released.
volume = ………………………………………….. cm3
(ii) Use Fig. 11.2 to find the time when the reaction finished.
time = ……………………………………………… s
(iii) The student repeats the experiment at a higher temperature.
On Fig. 11.2, sketch a line to show the results.
(iv) Increasing the temperature increases the rate of reaction.
State two other ways the student can increase the rate of the reaction.
1 ……………………………………………………………………………………..
2 …………………………………………………………………………………….
▶️Answer/Explanation
Ans : 11(a)(i) limestone does not pass through (the holes in) the filter paper and water does pass through (the holes in) the filter paper ;
limestone particles are larger / water particles are smaller (than the holes in the filter paper) ;
11(a)(ii) use universal indicator (paper / solution) ;
use colour to determine pH from chart ;
11(b)(i) combustion of carbon containing fuels ;
11(b)(ii) global warming / climate change ;
11(c)(i) 45 (cm3) ;
11(c)(ii) 190 (s) ;
11(c)(iii) steeper line ;
but levelling off at 45 (cm3) ;
11(c)(iv) decrease particle size / use powder / increase surface area ;
increase acid 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) Fig. 5.1 is a chart showing the composition of clean air.
Use your knowledge of the composition of clean air to determine the percentage of other gases in clean air.
Show your working.
percentage = …………………………………………….. %
(b) (i) Argon is one of the other gases in clean air.
Use the Periodic Table on page 24 to determine the electronic structure of an argon atom.
(ii) Use your answer to (b)(i) to explain why argon is very unreactive.
(iii) State one use for argon gas that depends on it being unreactive.
(c) (i) Small quantities of carbon dioxide are found in the air.
State one source of the carbon dioxide found in the air.
(ii) Carbon dioxide is a compound formed from the elements carbon and oxygen.
Describe the difference between an element and a compound.
(iii) Carbon dioxide is a greenhouse gas.
State the name of one other greenhouse gas.
(d) (i) Water is neutral.
State the pH value of pure water.
pH = …………………………………………………
(ii) Carbon dioxide in the air dissolves in rainwater. This causes the rainwater to become slightly acidic.
Suggest a pH value for this rainwater.
pH = …………………………………………………
▶️Answer/Explanation
Ans : 5(a) 78% and/or 21% seen ;
other gases = 1% ;
5(b)(i) 2,8,8 ;
5(b)(ii) full outer shell ;
5(b)(iii) lamps;
5(c)(i) combustion of fossil fuels ;
5(c)(ii) any one from (molecule of an) element contains only one type of atom ;
compound consists of atoms of two or more elements (bound together) ;
5(c)(iii) methane ;
5(d)(i) 7 ;
5(d)(ii) 4–6 ;
Question
(a) The list below shows some chemical processes.
chlorination chromatography cracking
crystallisation decomposition
electrolysis fractional distillation polymerisation
Identify the process from the list that is used:
(i) in the treatment of drinking water
…………………………………………………………………………………………………………………….
(ii) to separate a mixture of dyes
…………………………………………………………………………………………………………………….
(iii) to extract aluminium from bauxite
…………………………………………………………………………………………………………………….
(iv) to produce long chain molecules from monomer units.
…………………………………………………………………………………………………………………….
(b) When dilute hydrochloric acid is added to aqueous sodium hydroxide, a neutralisation reaction occurs.
Fig. 2.1 shows apparatus used to investigate the change in pH as the acid is added.
(i) State the name of apparatus A.
…………………………………………………………………………………………………………………….
(ii) State the reading on the pH meter when the dilute hydrochloric acid exactly neutralises
the aqueous sodium hydroxide.
…………………………………………………………………………………………………………………….
(iii) State the two products of the reaction shown in Fig. 2.1.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
(c) Describe what is observed when aqueous sodium hydroxide is added to blue copper(II) sulfate solution.
…………………………………………………………………………………………………………………………….
……………………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans: 2(a)(i) chlorination ;
2(a)(ii) chromatography ;
2(a)(iii) electrolysis ;
2(a)(iv) polymerisation ;
2(b)(i) burette ;
2(b)(ii) 7 ;
2(b)(iii) sodium chloride ;
water ;
2(c) pale blue precipitate ;