Question 1

Questions 1Which of the following pairs will give displacement reactions?NaCl solution and copper metalMgCl2 solution and aluminium metalFeSO4 solution and silver metalAgNO3 solution and copper metal.

Accepted Answer

AgNO3 solution and copperReason — In reactivity series, Na is above Cu, Mg is above Al and Fe is above Ag so displacement reaction does not occur in these pairs. Ag is below Cu, hence only AgNO3 solution and copper metal will give displacement reaction.

Question 2

Questions 2Which of the following methods is suitable for preventing an iron frying pan from rusting?Applying greaseApplying paintApplying a coating of zincAll of the above

Accepted Answer

Applying a coating of zincReason — Applying grease is not suitable as it will contaminate the food cooked in the frying pan making it inedible. Applying paint is not suitable as heating and washing the pan several times will cause the paint to peel off very soon. Hence, galvanisation i.e., applying a coating of zinc is the most suitable method to prevent an iron frying pan from rusting.

Question 3

Questions 3An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to beCalciumCarbonSiliconIron

Accepted Answer

CalciumReason — The resulting compound must be ionic as it has a high melting point which means that it must be formed by the reaction of a metal with oxygen. So, it will be either Calcium or Iron.As oxide of Calcium is soluble in water but oxides of Iron are not, hence the element is likely to be Calcium.

Question 4

Questions 4Food cans are coated with tin and not zinc becauseZinc is costlier than tinZinc has higher melting point than tinZinc is more reactive than tinZinc is less reactive than tin

Accepted Answer

Zinc is more reactive than tinReason — Zinc is more reactive than tin. It reacts with food acids to form poisonous compounds hence, it is not used to coat food cans.

Question 5

Questions 5You are given a hammer, a battery, a bulb, wires and switch.(a) How could you use them to distinguish between samples of metals and non-metals?(b) Asses the usefulness of these tests in distinguishing between metals and non-metals?

Accepted Answer

(a) Method 1 — On striking with hammer if the sample takes the shape of a sheet, it is a metal. A non-metal will break into pieces, hence, the two can be distinguished.Method 2 — Set up an electric circuit using a battery, a bulb, wires and switch as shown in the figure below.Place the element to be tested between the terminals A and B. If the bulb glows, then the sample is a metal, if not, then it is a non-metal.(b) Method 1 — When struck by hammer, metals being malleable turn into sheets whereas non-metals being brittle break into pieces.Method 2 — Metals are good conductors of electricity, hence the bulb glows whereas non-metals are poor conductors of electricity.

Question 6

Questions 6What are amphoteric oxides? Give two examples of amphoteric oxides.

Accepted Answer

Amphoteric oxides are those compounds which react with both acids and alkalis to form salt and water.Example: Zinc Oxide (ZnO), Lead Oxide (PbO)

Question 7

Questions 7Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Accepted Answer

Two metals which will displace hydrogen from dilute acidsZinc and Iron (as they are placed above hydrogen in reactivity series)Two metals which will not displace hydrogen from dilute acidsCopper and Silver (as they are placed below hydrogen in reactivity series)

Question 8

Questions 8In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Accepted Answer

Impure metal M is made the anode, thin strips of pure metal is made the cathode. A solution of metal salt is used as electrolyte.

Question 9

Questions 9Pratyush took sulphur powder on spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown below :(a) What will be the action of gas on(i) dry litmus paper?(ii) moist litmus paper?(b) Write a balanced chemical equation for the reaction taking place.

Accepted Answer

(a) The gas collected is sulphur dioxide. It is acidic in nature.(i) No change in colour is seen with dry litmus paper.(ii) moist blue litmus paper turns red, confirming that the acidic nature of the gas.(b) S (s) + O2 (g) ⟶ SO2 (g)

Question 10

Questions 10State two ways to prevent the rusting of iron.

Accepted Answer

Two ways to prevent the rusting of iron are:(i) Applying grease or paint.(ii) Galvanization.

Question 11

Questions 11What types of oxides are formed when non-metals combine with oxygen?

Accepted Answer

Acidic oxides are formed when non-metals combine with oxygen.

Question 12

Questions 12Give reasons :(a) Platinum, gold and silver are used to make jewellery.(b) Sodium, potassium and lithium are stored under oil.(c) Aluminium is highly reactive metal, yet it is used to make utensils for cooking.(d) Carbonate and sulphides ores are usually converted into oxides during the process of extraction.

Accepted Answer

(a) Platinum, gold and silver are low reactive metals so they rarely corrode and hence do not lose their shine and lustre. Additionally, they are very malleable and ductile so they can be easily crafted into beautiful jewellery having fine design.(b) Sodium, potassium and lithium react so vigorously with oxygen that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are stored under oil.(c) Aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide on its surface. This oxide layer is very stable and acts as a protective coating by preventing further reaction of aluminium. This combined with aluminium's excellent heat conductivity, easy and cheap availability, malleability and ductility makes it a good choice to make utensils for cooking.(d) As metals can be easily extracted by the reduction of their oxides rather than from their carbonates and sulphides therefore carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Question 13

Questions 13You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Accepted Answer

When copper vessels come into contact with moist carbon dioxide in the air, copper carbonate is formed that gets deposited as a green layer on the surface of these copper vessels and tarnishes them. The citric acid present in lemon or tamarind juice acts to neutralize the basic copper carbonate, effectively dissolving this layer. This restores the characteristic luster of the copper vessels.

Question 14

Questions 14Differentiate between metal and non-metal on the basis of their chemical properties.

Accepted Answer

Chemical propertiesMetalsNon-metalsReaction with oxygenforms basic oxidesforms acidic or neutral oxidesReaction with waterforms metal oxide and releases hydrogen gasdo not react with waterReaction with dil. acidsforms metal salts and releases hydrogen gasdo not react with dil. acidsReaction with Chlorineforms chlorides that are electrovalentforms chlorides that are covalent

Question 15

Questions 15A man went door to door posing as a goldsmith. He promised to bring back the glitter of the old and dull ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

Accepted Answer

The man's actions and the outcome suggest that he used aqua regia to clean the gold bangles. Aqua regia is a mixture of one part by volume of concentrated nitric acid and three parts by volume of concentrated hydrochloric acid. It is known for its ability to dissolve noble metals like gold and platinum.When the man dipped the bangles in aqua regia, outer layer of gold dissolved in it. So, although the bangles sparkled like new but their weight was reduced drastically.

Question 16

Questions 16Give reasons, why copper is used to make hot water tanks and not steel (an alloy of iron).

Accepted Answer

Copper being below hydrogen in the reactivity series does not react with cold water, hot water or steam. However, iron reacts with steam. If the hot water tanks are made of steel (an alloy of iron), then iron would react vigorously with the steam formed from hot water as shown in the reaction below:3Fe (s) + 4H2O (g) ⟶ Fe3O4 (s) + 4H2 (g)Thus, to prevent corrosion, copper is used to make hot water tanks and not steel.

Question 17

Question 1Give an example of metal which(i) is a liquid at room temperature.(ii) can be easily cut with knife.(iii) is best conductor of heat.(iv) is poor conductor of heat.

Accepted Answer

(i) Mercury(ii) Sodium(iii) Silver(iv) Lead

Question 18

Question 2Explain the meaning of malleable and ductile.

Accepted Answer

Malleable — Ability of metals to be beaten into thin sheets is called Malleability. Gold and silver are the most malleable metals.Ductile — Ability of metals to be drawn into thin wires is called ductility. Gold is the most ductile metal.

Question 19

Question 1Why is sodium kept immersed in kerosene oil?

Accepted Answer

Sodium reacts so vigorously with oxygen present in air that it catches fire if kept in the open. Hence, to protect it and to prevent accidental fires sodium is kept in kerosene oil.

Question 20

Question 2Write equation for the reaction ofiron with steamcalcium and potassium with water

Accepted Answer

3Fe (s) + 4H2O (g) ⟶ Fe3O4 (s) + 4H2 (g)Ca (s) + 2H2O (l) ⟶ Ca(OH)2 (aq) + H2 (g)2K (s) + 2H2O (l) ⟶ 2KOH (aq) + H2 (g) + heat energy

Metals and Non-metals

Exercises

Intext Questions 1

Intext Questions 2

Intext Questions 3

Intext Questions 4

Intext Questions 5