assignment no - 3
multiple choice questions
Chemical Reaction and Equations

1. Magnesium ribbon is cleaned before burning. why?
A. It absorbs moisture from the atmosphere which interferes with burning.
B. It’s outer layer form oxides which interfere with burning.
C. Dust from the atmosphere prevents its burning.
D. All of the above

2. Balanced equation of  Fe + H2O ———–> Fe3O4 + H2 is
A. Fe + 4H2O ———–> Fe3O4 + H2
B. Fe + 4H2O ———–> Fe3O4 + 4H2
C. 3Fe + 4H2O ———–> Fe3O4 + 4H2
D. 3Fe(s) + 4H2O(l) ———–> Fe3O4(s) + 4H2(g)

3. what is the formula of quick lime. what does it form when put into water.
A. CaO, CaCO3                                       B. CaO, Ca(OH)2
C. Ca(OH)2, CaCO3                                D. None

4. A compound used for white washing is
A. Quick lime                                         B. Slaked Lime
C. Blue vitriol                                         D. Limestone

5. Electrolysis of water is
A. Combination reaction                        B. Decomposition reaction
C. Displacement reaction                      D. None

6. Example of displacement reaction is
A. Fe(s) + CuSO4(aq)  ——>  FeSO4(aq) + Cu(s)
B. C(s) + O2(g)  ——–> CO2(g)
                      Sunlight
C. AgCl(s)  ———> 2Ag(s) + Cl2(g)
D. None

7. Lead nitrate Pb(NO3)2 on heating forms lead oxide (PbO) solid and nitrogen dioxide gas. what is the colour of lead oxide and nitrogen dioxide?
A. White, Colourless                             B. White, Brown
C. Yellow, Brown                                   D. Yellow, Colourless

8. Silver chloride on exposure to sunlight decomposes into silver and chlorine gas. this property is used in
A. Heat production as enormous energy is released.
B. Silver extraction as earth contains silver mainly in silver chloride form.
C. Photography as formed grey silver form an image imprint.
D. None

9. Quick lime is used in whitewashing because
A. It is cheap
B. It forms slaked lime with water which has a nice colour.
C. It forms slaked lime with water which reacts with atmospheric carbon dioxide to form limestone.
D. None

10. Example of a double displacement reaction will be
A. Metal with a salt                                B. Metal with an acid
C. Metal with metal                                D.  Salt with a salt

11. A reaction of hydrogen with oxygen to form water is a
A. Endothermic reaction                        B. Exothermic reaction
C. Decomposition reaction                    D. Reaction not feasible

12. Ferrous sulfate solution is green while ferric oxide formed by its decomposition is
A. Red                                                  B. White
C. Brown                                              D. Yellow

13. Corrosion or rusting of iron metal is
A. Oxidation of iron                                B. Reduction of iron
C. Displacement of iron                         D. None

14. Rancidity of fat or oil is:
A. Degradation by microorganism           B. Oxidation of fat
C. Reduction of fat                                   D. None

15. To facilitate the electrolysis of water we add a few drops of acids like sulfuric acid or salts like nacl. because:
A. It acts as a catalyst                            B. It prevents the decomposition of electrodes used.     
C. It increases the electrical conductivity of water.       D. None

16. Food manufacture pack fried foods with which gas to prevent oxidation of fat?
A. Oxygen                                            B. Nitrogen
C. Any of the above                               D. None

17. The oxidation reaction is:
A. Addition of oxygen atom                    B. Removal of the hydrogen atom
C. Loss of electron                                 D. All

18. When dilute hydro-chloric acid is added to granulated zinc placed in a test tube, the observation made is:
A. The surface of the metal turns shining
B. The reaction mixture turns milky
C. Odour of chlorine is observed
D. A colourless and odourless gas evolves with bubbles

19. When an aluminium strip is kept immersed in freshly prepared ferrous sulphate solution taken in a test tube, the change which is observed is:
A. Light green solution slowly turns colourless
B. The lower end of the test tube becomes slightly warm
C. A colourless gas with smell of burning sulphur is observed
D. Light green solution changes to blue



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