A more reactive metal can displace a less reactive metal from its oxide. Among Zinc, Magnesium, and Copper metals, magnesium is the most reactive, copper is the least reactive metal and zinc is less reactive .The displacement reaction will take place in the following cases

Metal	Zinc	Magnesium	Copper
Zinc Oxide	–	Displacement	–
Magnesium Oxide	–	–	–
Copper Oxide	Displacement	Displacement	–

Question - 14 : - Which metals do not corrode easily?

Answer - 14 : - Gold and platinum are the metals which do not corrode easily

Question - 15 : - What are alloys?

Answer - 15 : - An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

Question - 16 : - Which of the following pairs will give displacement reactions?

Answer - 16 : -

(a) NaCl solution and copper metal

(b) MgCl2 solution and aluminium metal

(c) FeSO4 solution and silver metal

(d) AgNO3 solution and copper metal

Answer

Option d i.e AgNO₃ solution and copper is correct answer. Copper displace the silver cations (reducing them to the elemental metal), in the process copper itself being oxidised to Copper II cations (Cu₂⁺) and going into solution. So silver metal precipitating out and a copper II nitrate solution will be remaining.

Cu(s) + 2AgNO₃ (aq) → Cu(NO₃)₂ (aq)+ 2Ag (s)

Question - 17 : - Which of the following methods is suitable for preventing an iron frying pan from rusting?

Answer - 17 : -

1. Applying grease

2. Applying paint

3. Applying a coating of zinc

4. All of the above

Answer

Answer is (c) Applying a coat of Zinc

Though applying grease and applying paint prevents iron from rusting but we cannot apply these methods on frying pan hence applying a coat of Zinc is most appropriate method to prevent an iron pan from rusting.

Question - 18 : - An element reacts with oxygen to give a compound with a high melting point.

Answer - 18 : -

This compound is also soluble in water. The element is likely to be

(a) Calcium

(b) Carbon

(d) Iron

Answer

Correct answer is option (a) i.e Calcium.

Calcium reacts with oxygen to give calcium oxide. Calcium oxide is soluble in water to give Calcium Hydroxide.

Carbon forms carbon-oxide with oxygen which is gas hence option B is wrong

Silicon reacts with oxygen and forms silicon dioxide. This is insoluble in water. So option C is not correct.

Iron reacts with oxygen and forms Iron dioxide. This is insoluble in water. So option D is not correct.

Question - 19 : - Food cans are coated with tin and not with zinc because

Answer - 19 : -

(a) Zinc is costlier than tin.

(b) Zinc has a higher melting point than tin.

(c) Zinc is more reactive than tin.

(d) Zinc is less reactive than tin.

Answer is c. Food cans are coated with tin and not with zinc because Zinc is more reactive that is electro positive than tin.

Question - 20 : - You are given a hammer, a battery, a bulb, wires and a switch.

Answer - 20 : -

(a) How could you use them to distinguish between samples of metals and non-metals?

(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Answer

1. Metals are malleable and can be easily drown into sheets by hitting with hammer. On the other hand if we beat non-metals they break down and they cannot be drawn into sheets as they are non-malleable. Metals of good conductors of electricity hence they make bulb when you connect metals with a battery, wire and bulb. Similarly If non-metals are bad conductors of electricity chance they fail to lit up the bulb on connecting with wire and battery.

2. These experiments can be helpful to demonstrate the malleability and electric conductivity of the metals and non-metals

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Chapter 3– Metals and Non Metals Solutions

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