1
A student is observing an experiment where a metal is reacted with dilute hydrochloric acid. They notice vigorous bubbling and a significant rise in the temperature of the solution. Based on these observations, which of the following metals is most likely being used?(a) Copper(b) Silver(c) Magnesium(d) Gold1mark
2
An old Indian temple has a bronze statue that has remained largely unaffected by corrosion over centuries, while an iron pillar nearby shows signs of rusting.(a) Explain why bronze is more resistant to corrosion than iron. [2 marks](b) Name the components of bronze. 1mark
3
A student performs an experiment where a metal wire is heated and a pin attached to its free end with wax falls off. This demonstrates that the metal is a good conductor of heat. Which of the following metals is most likely being tested?(a) Sulphur(b) Aluminium(c) Graphite(d) Iodine1mark
4
Assertion (A): Metals like sodium and potassium are stored under kerosene.Reason (R): Sodium and potassium react vigorously with oxygen and moisture present in the air, leading to fire.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.1mark
5
A metal oxide when dissolved in water forms an alkali. This metal oxide is likely to be:(a) Aluminium oxide(b) Zinc oxide(c) Sodium oxide(d) Copper oxide1mark
6
A scientist is investigating the properties of different elements. She finds an element that is lustrous, malleable, and ductile, and it conducts heat and electricity. She also finds that it reacts with oxygen to form a basic oxide. Which of the following elements is she most likely studying?(a) Sulphur(b) Carbon(c) Iron(d) Chlorine1mark
7
Assertion (A): Ionic compounds conduct electricity in the molten state.Reason (R): In the molten state, ions in ionic compounds are free to move and carry electric charge.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.1mark
8
Consider the following reactivity series: K, Na, Ca, Mg, Al, Zn, Fe, Pb, [H], Cu, Hg, Ag, Au.A metal 'X' displaces hydrogen from dilute acids but does not displace any other metal from its salt solution when compared with metals Y and Z, where Y is less reactive than X and Z is more reactive than X.(a) Arrange X, Y and Z in decreasing order of reactivity. [2 marks](b) Give an example of a metal that would displace 'X' from its salt solution. 1mark
9
An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. It is prepared by first melting the primary metal, and then dissolving the other elements in it in definite proportions.(a) Name an alloy which is used to make electrical wires and has a low melting point. [1 mark](b) Brass, an alloy of copper and zinc, is not a good conductor of electricity, whereas copper is used for making electrical circuits. Explain this observation. 2marks
10
Case Study: Extraction of MetalsMetals are extracted from their ores. The process depends on the reactivity of the metal. Metals like gold, silver, and platinum are found in the native state because they are least reactive. Metals like sodium, potassium, and calcium are very reactive and are found in combined states, usually as oxides. Metals in the middle of the reactivity series, like iron and zinc, are moderately reactive and are found as oxides, sulphides, or carbonates.(a) Why are metals like gold and silver found in the free state? [1 mark](b) Why are metals like sodium and potassium not found in the free state? [1 mark](c) Explain why it is easier to obtain a metal from its oxide than from its sulphide or carbonate ore. 2marks
11
A student is asked to identify an unknown metal. They observe that it tarnishes in moist air and forms a green layer. This is characteristic of the corrosion of which metal?(a) Iron(b) Silver(c) Aluminium(d) Copper1mark
12
Assertion (A): Diamond is the hardest natural substance and is an allotrope of carbon.Reason (R): Graphite, another allotrope of carbon, is a good conductor of electricity.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.1mark
13
A metal, when heated in air, forms a metal oxide that shows both acidic and basic properties. This type of metal oxide is known as:(a) Basic oxide(b) Acidic oxide(c) Amphoteric oxide(d) Neutral oxide1mark
14
A piece of wire made from a metal is found to be very thin and can be drawn into wires without breaking. This property is called:(a) Malleability(b) Ductility(c) Sonority(d) Conductivity1mark
15
Case Study: Properties of Ionic CompoundsIonic compounds are formed by the transfer of electrons between metals and non-metals. They generally have high melting and boiling points due to strong electrostatic forces between oppositely charged ions. They are usually soluble in water and insoluble in organic solvents. In solid-state, they do not conduct electricity, but they do conduct electricity in the molten state or when dissolved in water.(a) Why do ionic compounds have high melting and boiling points? [2 marks](b) Explain why ionic compounds conduct electricity in the molten state but not in the solid state. 2marks
16
Two metals, A and B, react with dilute hydrochloric acid. Metal A reacts vigorously, producing a large amount of gas and heat, while metal B reacts slowly, producing fewer bubbles and no noticeable heat.(a) Which metal, A or B, is more reactive? Justify your answer. [2 marks](b) Name one metal that could behave like metal B and one metal that would not react with dilute HCl. 2marks
17
Assertion (A): Aluminium is used to make cooking utensils despite being a reactive metal.Reason (R): Aluminium forms a protective oxide layer on its surface when exposed to air, which prevents further corrosion.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true.1mark
18
A scientist is trying to extract a metal from its ore. The ore is a metal sulphide. The scientist first heats the ore strongly in the presence of excess air. This process converts the sulphide ore into a metal oxide. What is this process called?(a) Calcination(b) Roasting(c) Reduction(d) Electrolytic refining1mark
19
Case Study: Corrosion PreventionRusting of iron can be prevented by various methods. Painting and oiling create a barrier between iron and air/moisture. Galvanization involves coating iron with a more reactive metal, zinc, which preferentially corrodes, protecting the iron. Alloying with metals like chromium and nickel to form stainless steel also prevents rusting.(a) Explain why galvanization protects iron even if the zinc coating is scratched. [2 marks](b) Why is pure iron not used for making everyday objects like spoons and frying pans? [1 mark](c) Name one method used to prevent the rusting of iron that involves making an alloy. 1mark
20
A student observes a chemical reaction where a copper wire is placed in a solution of iron(II) sulphate. After some time, no reaction is observed. Which of the following can be concluded from this observation?(a) Copper is more reactive than iron.(b) Copper is less reactive than iron.(c) Copper and iron have the same reactivity.(d) Copper reacts with iron(II) sulphate to form iron and copper(II) sulphate.1mark
Answers
1
(c) Magnesium. Magnesium is a reactive metal that reacts vigorously with dilute acids, producing hydrogen gas and significant heat. Copper, silver, and gold are less reactive metals and would not show such a vigorous reaction.
2
(a) Bronze is an alloy of copper and tin. Copper and tin are less reactive metals compared to iron. Iron reacts with moist air to form rust (iron oxide), while copper forms a protective green layer of basic copper carbonate. This makes bronze much more resistant to corrosion than iron.(b) Bronze is an alloy of copper and tin.
3
(b) Aluminium. Aluminium is a metal known to be a good conductor of heat. Sulphur and graphite are non-metals (though graphite conducts electricity, it's not typically used in wire form for heat conductivity tests like this). Iodine is also a non-metal. The activity described relates to the physical property of heat conductivity in metals.
4
(a) Both A and R are true and R is the correct explanation of A. Sodium and potassium are highly reactive metals that react with oxygen and moisture in the air. To prevent this reaction and potential fire hazards, they are stored submerged in kerosene oil.
5
(c) Sodium oxide. Metal oxides that dissolve in water to form alkalis are typically oxides of alkali metals like sodium and potassium. Aluminium oxide and zinc oxide are amphoteric, and copper oxide is basic but generally insoluble in water.
6
(c) Iron. Iron is a metal that is lustrous, malleable, ductile, and a good conductor of heat and electricity. It also reacts with oxygen to form iron(III) oxide, which is a basic oxide. Sulphur and carbon are non-metals. Chlorine is a non-metal.
7
(a) Both A and R are true and R is the correct explanation of A. In the molten state or in aqueous solution, the ions in ionic compounds are mobile and can carry charge, leading to electrical conductivity. In the solid state, the ions are held in a fixed lattice structure and cannot move.
8
(a) The order of reactivity is Z > X > Y. Metal X displaces hydrogen from dilute acids, placing it above hydrogen in the reactivity series. Metal Y does not displace hydrogen from dilute acids, placing it below hydrogen. Metal Z is more reactive than X and would displace X from its salt solution. Metals less reactive than X would not displace X.(b) Any metal from the reactivity series that is above X (e.g., K, Na, Ca, Mg, Al).
9
(a) Solder. Solder is an alloy of lead and tin and has a low melting point, making it suitable for welding electrical wires.(b) Brass is an alloy of copper and zinc. While copper is a good conductor, the presence of zinc in brass changes its properties, making it a poorer conductor of electricity compared to pure copper. This is because alloys have different electrical conductivities than their constituent pure metals due to altered electron mobility.
10
(a) Gold and silver are found in the free state because they are very unreactive metals and do not readily form compounds with other elements.(b) Metals like sodium and potassium are highly reactive and readily combine with elements like oxygen and chlorine, hence they are never found in the free state in nature.(c) Metal oxides can be more easily reduced to the pure metal by heating with a reducing agent like carbon compared to their sulphide or carbonate ores. Sulphide ores are first converted to oxides by roasting, and carbonate ores are converted to oxides by calcination, before reduction.
11
(d) Copper. Tarnished copper vessels develop a green layer due to the formation of basic copper carbonate when copper reacts with moist carbon dioxide in the air. Iron rusts to form a reddish-brown flaky substance, silver tarnishes to a black coating of silver sulphide, and aluminium forms a dull grey protective oxide layer.
12
(a) Both A and R are true and R is the correct explanation of A. Diamond is the hardest allotrope of carbon due to its rigid tetrahedral structure. Graphite is a good conductor of electricity because of its layered structure with delocalized electrons.
13
(c) Amphoteric oxide. Amphoteric oxides are metal oxides that react with both acids and bases to form salt and water. Examples include aluminium oxide () and zinc oxide ().
14
(b) Ductility. Ductility is the property of a metal that allows it to be drawn into thin wires without breaking. Malleability refers to the ability to be beaten into thin sheets.
15
(a) Ionic compounds have high melting and boiling points because strong electrostatic forces of attraction exist between the positively charged cations and negatively charged anions in their crystal lattice. A large amount of energy is required to overcome these strong forces and break the ionic bonds.(b) In the solid state, the ions in ionic compounds are held in fixed positions within the crystal lattice and are not free to move. Therefore, they cannot conduct electricity. In the molten state or when dissolved in water, the ionic bonds are weakened or broken, allowing the ions to become mobile. These mobile ions can then move towards the oppositely charged electrodes, carrying electric current and thus conducting electricity.
16
(a) Metal A is more reactive than metal B. The vigorous bubbling and significant heat production (exothermic reaction) observed with metal A indicate a rapid reaction with dilute hydrochloric acid, signifying high reactivity. Metal B reacts slowly, indicating lower reactivity.(b) Metal B could be iron or zinc, which react less vigorously with dilute HCl than magnesium. Metals like copper, silver, or gold would not react with dilute HCl.
17
(a) Both A and R are true and R is the correct explanation of A. Aluminium is a reactive metal, but it forms a protective layer of aluminium oxide () on its surface when exposed to air. This layer is strong and adheres well to the metal, preventing further oxidation and corrosion, thus making it suitable for cooking utensils.
18
(b) Roasting. Roasting is the process of heating a sulphide ore strongly in the presence of excess air to convert it into its metal oxide. Calcination is the process of heating a carbonate ore strongly in the absence or limited supply of air to convert it into its metal oxide.
19
(a) Galvanization protects iron even if the zinc coating is scratched because zinc is more reactive than iron. Zinc preferentially corrodes (acts as a sacrificial anode) and protects the iron from rusting. This is known as sacrificial protection.(b) Pure iron is very soft and stretches easily when hot, making it unsuitable for making everyday objects like spoons and frying pans which require hardness and durability.(c) Stainless steel is an alloy of iron, chromium, and nickel, and it is used to prevent rusting.
20
(b) Copper is less reactive than iron. In a displacement reaction, a more reactive metal can displace a less reactive metal from its salt solution. Since copper does not displace iron from iron(II) sulphate solution, it indicates that copper is less reactive than iron.
