Text-book Questions with Solution:
NCERT Book Page 40
Q1: Give an example of a metal which
(i) is a liquid at room temperature.
(ii) can be easily cut with a knife.
(iii) is the best conductor of heat.
(iv) is a poor conductor of heat.
Answer:
(i) Metal that exists in liquid state at room temperature is Mercury.
(ii) Metals that can be easily cut with a knife are Sodium and Potassium
(iii) Metals that are the best conductor of heat are Silver and Gold
(iv) Metals that are poor conductors of heat are Mercury and lead.
Q2. Explain the meanings of malleable and ductile.
Answer:
Meliable: Some metals can be beaten into thin sheets by beating such substances are called malleable.
Ductile: Some substances can be drawn into thin wires such substances are called ductile.
Page No. 46
Q1. Why is sodium kept immersed in kerosene oil?
Answer: Sodium and potassium are highly reactive metals, they react with air and catch fire easily, so sodium is kept immersed in kerosene.
Q2. Write equation for the reactions of
(i) iron with steam
(ii) calcium and potassium with water
Answer:
(i) 3Fe(s)+ 4H2O(g)→ Fe3O4+4H2(g) |
(ii) Ca(s)+2H2O(I)→ Ca(OH)2 (aq)+H2(g) |
Q3. Samples of four metals A, B, C, and D were taken and added to the following solution one by one. The results obtained have been tabulated as follow:
Use the table above to answer the following questions about meals A,B,C and D.
(i) Which is the most relative metal?
(ii) What would you observe of B is added to a solution of copper (II) sulphate.
(iii) Arrange the metals A,B,C and D in the order of decreasing reactivity.
Answer: (i) Metal B is more reactive metal.
(ii) displacement reaction will take place.
(iii) Metal B > Metal A > Metal C > Metal D
Q4. Which gas is produced when dilute hydrochlroic acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
Answer: Hydrogen gas is released.
Fe (s) + H2SO4 → FeSO4 (aq) + H2 (g)
Q5. What would you observe when zinc is added to a solution of Iron(II) sulphate? write the chemical reaction that takes place?
Answer: Zinc displaces iron from iron sulphate solution.
Zn + FeSO4 → ZnSO4 + Fe
Page no. 49
Q1. (i) Write the electric-dot structure for sodium, oxygen and magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compound?
Q2. Why do ionic compound have high melting points?
Answer: The mutual ionic attraction is very strong in an ionic compound. It takes a lot of energy to break this powerful bond. Hence their melting point is high.
Page no. 53
Q1. Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue
Answer: (i) Minerals are those substances in which metals are found in the form of their compounds.
(ii) Such minerals in which the extraction of metals is very easy and suitable are called ores.
(iii) Minerals are not found pure in nature, the impurities present in them are called gangue.
Q2. Name two metals which are found in nature in the free state.
Answer: Gold and Platinum.
Page no. 55
Q1.Metalic oxides of zinc, magnesium and copper were heated with the following metals.
| Metal | zinc | magnesium | copper |
| zinc oxides | |||
| magnesium oxides | |||
| copper oxides |
In which case will you find displacement reactions taking place?
Answer:
| Metal | zinc | magnesium | copper |
| zinc oxides | no | yes | no |
| magnesium oxides | no | no | no |
| copper oxides | yes | no |
Q2. In which metal do not corrode easily?
Answer: Gold, Platinum and Silver.
Q3. What are alloys?
Answer: A homogeneous mixture of two or more metals is called an alloy.
