CIE iGCSE Co-Ordinated Science C9.6 Extraction of metals Exam Style Questions Paper 3
Question
(a) A student investigates the rate of reaction between calcium carbonate and hydrochloric acid.
The student does the experiment four times and each time uses:
• the same mass of calcium carbonate
• different sizes of calcium carbonate pieces
• a different concentration of hydrochloric acid.
Table 5.1 shows the four experiments, A, B, C and D.
(i) State which experiment has the fastest rate of reaction.
experiment …………………………………………….
(ii) The student measures the rate of reaction by timing how long it takes for the calcium carbonate pieces to disappear.
Suggest the piece of apparatus the student uses to measure a time of 100s.
…………………………………………………………………………………………………………………….
(b) The student wants to determine the pH of the acid. She puts some universal indicator paper into the acid.
(i) Describe how the student uses the colour of the universal indicator paper to determine the pH of the hydrochloric acid and its relative acidity.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(ii) Suggest the pH of dilute hydrochloric acid.
pH = …………………………………………….
(c) Hydrogen chloride, HCl, dissolves in water to make hydrochloric acid.
(i) Complete the dot-and-cross diagram in Fig. 5.1 to show the bonding in a molecule of hydrogen chloride.
Only show the outer shell electrons.
(ii) State the name of this type of chemical bonding.
……………………………………………………………………………………………………………………………….
(d) Hydrogen chloride is a gas. Water is a liquid.
Describe the difference in the structure between a liquid and a gas, in terms of particle separation and the motion of the particles.
particle separation ……………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………
motion ………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans: 5(a)(i) experiment D ;
5(a)(ii) stopwatch ;
5(b)(i) check colour against pH chart ;
red pH 1–3 very acidic and orange/yellow pH 4–6 weakly acidic ;
5(b)(ii) pH = any value between 1 and 6 ;
5(c)(i)
1 shared pair only ;
all else correct ;
5(c)(ii) covalent (bonding) ;
5(d) (liquid) closer together / (gas) further apart) ;
(liquid) slide past each other / slower / (gas) free to move / faster ;
Question
(a) (i) An iron nail rusts when it is exposed to damp air.
Rusting involves the oxidation of iron.
State what is meant by the term oxidation.
(ii) Describe one method used to prevent the iron nail from rusting.
Explain how this method prevents the iron nail from rusting.
method …………………………………………………………………………
explanation …………………………………………………………………………
(b) Complete the sentence.
Metal ores are a finite resource and therefore, metals need to be ……………………………… .
(c) Iron is a transition element.
Put a tick (3) in the boxes next to all the correct statements about iron.
(d) Steel is an alloy of iron.
(i) Suggest why steel is used for making cars instead of pure iron.
(ii) Table 2.1 shows the percentage composition of stainless steel.
Calculate the mass of iron contained in 80 kg of stainless steel.
mass of iron = ……………………………………………. kg
(e) Iron is malleable.
State the meaning of malleable.
▶️Answer/Explanation
Ans : 2(a)(i) gain of oxygen ;
2(a)(ii) paint it ;
stops contact with air and water ; etc.
2(b) recycled ; OWTTE
2(c) iron acts as a catalyst ;
iron forms coloured compounds ;
2(d)(i) stronger ;
2(d)(ii) iron % 65 ;
80 × 65 / 100 = 52 (kg) ;
2(e) can be shaped or bent ;
Question
(a) The list gives the names of six compounds.
aluminium oxide
ammonium nitrate
carbon dioxide
lead bromide
sodium chloride
sulfur dioxide
Answer the questions about these compounds.
Each compound may be used once, more than once or not at all.
State which compound:
(i) has the formula PbBr2.
(ii) is a salt from which ammonia can be displaced.
(iii) is an acidic oxide.
(iv) is a greenhouse gas.
(v) is the main constituent of bauxite.
(b) Aluminium, copper and iron are all solid metals.
State three general physical properties of solid metals.
1 …………………………………………………………………………
2 …………………………………………………………………………
3 …………………………………………………………………………
(c) (i) Duralumin is an alloy of aluminium.
Table 2.1 shows the percentage composition of duralumin.
Calculate the mass of aluminium in 20 kg of duralumin.
mass of aluminium = ……………………………………………. kg
(ii) Table 2.2 shows the melting points of aluminium, copper, magnesium and duralumin.
Duralumin does not have a precise melting point but melts over a range of temperatures.
Explain why duralumin does not have a precise melting point.
▶️Answer/Explanation
Ans : 2(a)(i) lead bromide ;
2(a)(ii) ammonium nitrate ;
2(a)(iii) carbon dioxide / sulfur dioxide ;
2(a)(iv) carbon dioxide ;
2(a)(v) aluminium oxide ;
2(b) any three from:
conducts heat ;
conducts electricity ;
malleable ;
high melting/boiling point ;
2(c)(i) 95 / 100 × 20 = 19 (kg) ;
2(c)(ii) because it is not a pure substance / it is a mixture ;
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
Thermal decomposition happens when compounds are heated and break down into simpler substances.
(a) Limestone thermally decomposes to produce lime in a lime kiln.
Fig. 5.1 shows a lime kiln.
(i) State the chemical names of limestone and lime.
▶️Answer/Explanation
Limestone: calcium carbonate
Lime: calcium oxide
(ii) Suggest why the limestone and carbon inside the lime kiln are in small pieces.
▶️Answer/Explanation
The limestone and carbon are in small pieces to increase the surface area, which speeds up the reaction rate by allowing more contact between the reactants.
(iii) Explain why farmers often treat soil with limestone.
▶️Answer/Explanation
Farmers treat soil with limestone to neutralize acidic soil, improving soil quality and making it more suitable for plant growth.
(b) Fig. 5.2 shows apparatus used for the thermal decomposition of sodium hydrogencarbonate.
When the sodium hydrogencarbonate in the test-tube is heated for several minutes, the following observations are made:
- A gas is released that turns limewater milky.
- The cobalt chloride paper changes colour from blue to pink.
- A different compound, sodium carbonate, remains in the test-tube.
(i) Use this information to complete the word equation for the thermal decomposition of sodium hydrogencarbonate.
▶️Answer/Explanation
sodium hydrogencarbonate → sodium carbonate + carbon dioxide + water
(ii) The mass of sodium carbonate that remains after the reaction is smaller than the original mass of sodium hydrogencarbonate.
Explain why.
▶️Answer/Explanation
The mass of sodium carbonate is smaller because gaseous products (carbon dioxide and water) are released during the reaction, reducing the total mass of the solid residue.
(c) Cracking of hydrocarbons is another example of thermal decomposition.
Fig. 5.3 shows the cracking of hydrocarbons.
(i) Both X and Y in Fig. 5.3 are mixtures of hydrocarbons.
Describe two ways in which molecules in mixture X are different from molecules in mixture Y.
▶️Answer/Explanation
1. Mixture Y contains unsaturated hydrocarbons (and X does not).
2. Molecules in mixture Y are smaller on average than those in mixture X.
(ii) Predict the change in colour, if any, when mixture Y is shaken with aqueous bromine.
▶️Answer/Explanation
The colour will change from orange to colourless.