1. What is an alloy?

An alloy is a material containing two or more  elements, at least one of which is a metal. Alloys are commonly prepared by fusing component elements. The properties of alloys differ in many respects from those of their components. Its components must be miscible in liquid state and non-separate on solidification. Its properties are intermediate between those of the metals composing them.

Example: Amalgam is an alloy in which the base metal is  mercury.

2. What is stainless steel?

Stainless steel is an alloy of iron which contains 75% iron ,15%chromium,10% nickel and .5% carbon. (Reason for alloying: nickel and chromium impart lustre and carbon imparts hardness ).

3. What is bell metal ?

Bell metal is a hard alloy used for making bells .It is a form of bronze , 78% copper and 22% tin.

4. Explain with example how metals react with acids.

Metals react with dilute acids to form hydrogen.

Example: Mg +2HCI →  MgCl₂+ H₂
                 Zn+H₂SO₄→   ZnSO₄ + H₂

5. What is meant by displacement reactions? Give example.

One metal  displacing another metal from its solution which has low electro positivity is known as displacement reaction.

Fe + CuSO₄ → Cu + FeSO₄

6. How does sodium react with air?

Sodium reacts with air and changes to sodium oxide and later to sodium carbonate.
               4Na + O₂ → 2Na₂O
              Na₂O + H₂O → 2NaOH
             2NaOH + CO₂ → Na₂CO₃+H₂O

7. How does sodium react with water?

Sodium reacts with water to form hydrogen. The aqueous product formed has alkaline nature. It is because that sodium hydroxide is formed.
              2Na + 2H₂O → 2NaOH + H₂

8. What happens when aluminium is exposed to air?

Aluminium get oxidised in air and the coating of aluminium oxide formed on this prevents further oxidation.

9. A, B, C, D are four test tubes containing ZnSO₄, CaCl₂, AgNO₃, FeCl₃. Cu is put into each test tube. In which of the solutions do Cu Introduce blue colour? Why?

   Only in the test tube containing AgNO₃ solution. Among the metals silver is the only metal which is placed below copper in the electrochemical series. So Cu can reduce the Ag ions in AgNO₃ solution. Copper atom loses 2 electrons and changes in to Cu²⁺ ions and dissolves in the solution. At the same time copper cannot reduce the ions of metals Zn, Ca, Fe etc. So there is no colour change in the solution.

10. What is the oxidation – reduction reactions when Zn rod is immersed in CuSO₄ solution?

   Oxidation reaction:
                 Zn → Zn²⁺ + 2^e-
Reduction reaction:
               Cu²⁺ + 2^e- → Cu
Redox reaction:
   Zn + Cu²⁺ SO₄^2-    →  Zn²⁺ SO₄^2- + Cu
  Cu   →  Cu²⁺  + 2^e-  ( reaction in Cu rod)
  Zn²⁺ 2^e-   →  (Zn²⁺  ion in solution become atom ) 
  Cu²⁺ + SO₄^2-  →  CuSO₄ ( Cu²⁺ ion which came to the solution combine with SO₄^2- ) 

11. What is the change that take place when Zn rod is dipped in ZnSO₄ and Cu in CuSO₄ solution?

     When a metal is immersed in a solution of its own, it displays a tendency to form ions by losing electrons. At the same time, metal ions in the solution show the tendency to form metal atom by accepting electrons. These changes can take place when Zn rod is dipped in ZnSO₄ and Cu rod in CuSO₄ solution. There is no observable change in  colour here. The reactions that takes place here are as follows:-
Zn rod: Zn  → Zn²⁺ + 2^e-
ZnSO₄ solution :  Zn²⁺ + 2^e-  → Zn
Cu rod : Cu  →  Cu²⁺ + 2^e-   
Cu SO₄ solution : Cu²⁺ + 2^e-  → Cu

12. The following table shows various electrodes connected through external circuit. Find out at which electrodes do oxidation and reduction take place, on the basis of electrochemical series.
   

13. Which flux is used for the extraction of iron? Which slag is produced? Write the chemical formula.

  The iron ore contains sand and other impurities.Lime stone (Ca CO₃) helps to remove these impurities. It is used as flux here. When lime stone (CaCO₃) decomposes at  high temperature CaO is formed and reacts with silica (SiO₂) to form calcium silicate.

CaCO₃  → CaO + CO₂
CaO + SiO₂  → CaSiO₃

14. Prepare a table showing the uses of Aluminium and the property made use of in each.

15. Answer the following questions which are related to the process of electrolysis used in the production of aluminium from alumina.

a. Give equation to represent the ionization of alumina
 Al₂O₃ → 2Al₃+  + 3O₂^2-

b. Name the ion reaching the anode.
  Ion : O₂^2-

c. What is the ion reaching the cathode? Name the element deposited here. Write the equations.
Ion  - Al³⁺ ; element - Al

d. Write equations for the reaction between the anode and the oxygen liberated there.
 C _(s)  + O_2(g) → CO_2(g)

16.Explain the different types of alloys and their components.

17. Based on the list of elements given, write chemical equations ?
Na, Al, Cu, Mg, Zn

a. Reaction of one of the metals with water
2Na + 2H₂O  → 2NaOH + H₂

b. Reaction of one of the metals with steam
Zn + H₂O → ZnO + H₂
c. Reaction with acid and one of the metals which do not react with water
  2AI + 3H₂SO₄ → AI₂(SO₄)₃ + 3H₂ 
d. Reaction of a metal salt with one of the metals.
 Fe  +  CuSO₄ → Cu + FeSO₄

18. We have to produce certain substances using alloys. The following things are to be produced. Which alloy will you select to produce each of them ? Why?
• Utensils
• Statues
• Filament in electric heater
• Body of aeroplane