14.2 METALS (W2) 2023 Answers

1 Beatty Secondary School Science Department (Chemistry Unit) Chemistry 6092 Name: ___________________________________ ( ) Date: _______________ Class: 3E___ TOPIC: REACTIVITY SERIES AND RUSTING (WORKSHEET 2) Learning Objectives: (a) Place in order of reactivity calcium, copper, (hydrogen), iron, lead, magnesium, potassium, silver, sodium and zinc by reference to (i) the reactions, if any, of the metals with water, steam and dilute hydrochlori c acid, (ii) the reduction, if any, of their oxides by carbon and/or by hydrogen. (b) Describe the reactivity series as related to the tendency of a metal to form its positive ion, illustrated by its reaction with (i) the aqueous ions of the other listed metals, (ii) the oxides of the other listed metals. (c) Deduce the order of reactivity from a given set of experimental results. (d) Describe the action of heat on the carbonates of the listed metals and relate thermal stability to the reactivity series. (e) Describe the essential conditions for the corrosion (rusting) of iron as the presence of oxygen and water; prevention of rusting can be achieved by placing a barrier around the metal, e.g. painting; greasing; plastic coating; galvanizing. (f) Describe the sacrificial protection of iron by a more reactive metal in terms of the reactivity series where the more reactive metal corrodes preferentially, e.g. underwater pipes have a piece of magnesium attached to them. Multiple-Choice Questions 1 Which element reacts with dilute hydrochloric acid to produce hydrogen? A carbon B copper C silver D zinc ( D ) 2 Which metal does not react with cold water but reacts when heated strongly in steam? A calcium B copper C iron D sodium ( C ) 3 Which oxide can be reduced to the metal by heating with carbon? A calcium oxide B magnesium oxide C potassium oxide D zinc oxide ( D )

2 4 The diagram shows metal T reacting with water. Which could metal T be? A calcium B copper C sodium D potassium ( A ) 5 Metal Z is placed between zinc and iron in the reactivity series. Which statement is likely to be correct? A A heated mixture of zinc and the oxide of Z will react. B Z will react quickly with cold water. C Iron will displace Z from an aqueous solution of its chloride. D Z will not react with hot dilute hydrochloric acid. ( A ) 6 Element M react in the following ways. M + 2HCl → MCl2 + H2 2M + O2 → 2MO MO + H2 → no reaction Which could element M be? A aluminium B calcium C copper D potassium ( B ) 7 Magnesium is placed in aqueous copper(II) sulfate. Which change is correct? A copper atoms lose electrons B copper ions lose electrons C magnesium atoms lose electrons D magnesium ions lose electrons ( C ) 8 An excess of zinc powder is added to a solution containing a mixture of the ions Mg 2+, Ca2+, Cu2+ and Ag+. Which metals will be displaced from the solution? A calcium and magnesium B copper and calcium C magnesium and silver D silver and copper ( D )

3 9 The corrosion of underground steel pipes can be prevented by sacrificial protection. This is shown in the diagram. Which element is most suitable for use as sacrificial element P? A carbon B copper C magnesium D silver ( C ) 10 The table shows the results of tests to compare the reactivity for metals X, Y and Z. Test Results metal X metal Y metal Z Does carbon reduce the metal oxide? yes no yes Does the metal react with hydrochloric acid to produce hydrogen gas? yes yes no What is the order of reactivity of the metals? most reactive least reactive A Y X Z B Z X Y C Z Y X D Y Z X ( A ) 11 In which test-tube is the iron least likely to rust? A B C D ( D )

4 12 Four experiments on rusting are shown. Which two experiments can be used to show that air is needed for iron to rust? A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4 ( C ) 13 Three experiments to compare the reactivities of three metals are shown in the diagram. What is the correct order of reactivity for the three metals? most reactive least reactive A cobalt manganese tin B manganese cobalt tin C manganese tin cobalt D tin cobalt manganese ( B )

5 14 In the experiment shown in the diagram, steam is passed over a heated solid P. Gas Q is collected. What are substances P and Q? P Q A copper hydrogen B lead oxygen C silver oxygen D zinc hydrogen ( D ) 15 Copper(II) oxide is reduced to copper as shown. The burner is then turned off but the hydrogen is kept flowing until the tube is cold. What is the main reason why hydrogen is kept flowing? A to lessen the risk of explosion in the hot tube B to make certain that the reaction is complete C to prevent the copper from reacting with the air D to remove traces of water left in the tube ( C ) 16 Which is correct, comparing calcium and iron? ease of metal in giving up electrons ease of decomposition of the metal carbonate when heated A greater for calcium than for iron greater for calcium than for iron B greater for calcium than for iron greater for iron than for calcium C greater for iron than for calcium greater for calcium than for iron D greater for iron than for calcium greater for iron than for calcium ( B )

6 17 Compound X decomposes when heated to give a black solid and a colourless gas. What could X be?? A calcium carbonate B copper(II) carbonate C magnesium carbonate D sodium carbonate ( B ) 18 The carbonate of metal X is a white solid. It decomposes when heated to form carbon dioxide and a yellow solid. What is metal X? A copper B lead C iron D sodium ( B ) Structured Questions 19 The reaction between aluminium and iron( III) oxide can be used to join lengths of steel railway tracks. This reaction is known as the thermit reaction. The equation for the thermit reaction is given below. Fe2O3(s) + 2Al(s) → Al2O3(s) + 2Fe(l) (a) (i) What does (l) after the Fe in the chemical equation mean? liquid / molten state (ii) Why does the aluminium react with the iron(III) oxide? Aluminium is more reactive than iron. As such, aluminium displaces / reduces iron from iron(III) oxide. (iii) Suggest why the thermit reaction can be used to join lengths of railway track. Thermit reaction is exothermic, hence it releases large amounts of heat energy, which is used to weld railway lines together where molten iron flows into the gaps between rails, joining them tightly together. (b) Calculate the mass of aluminium required to react with 640 g of iron(III) oxide No of mol of Fe2O3 = 640 160 = 4.00 mol Compare mole ratio: Fe2O3 : Al 1 : 2 4 : 8 Mass of Al = 8 × 27 = 216 g

7 20 The effects of water on five metals A, B, C, D and E, are given in the table. metal effect of water A Reacts very slowly when placed in boiling water. The hot metal burns in steam with a white flame. B Explodes with cold wa