Class 9th Chemistry Unit 7 Electrochemistry

chemistry 9th notes Chapter No 7

1. Oxidation number of all elements is free state is:


2. Which electrolyte is used in electroplating of zinc?  


3. The branch of chemistry that deals with relationship between electricity and chemical reactions is:


4. Sterling silver is an alloy of silver and:


5. In the formation of water from hydrogen and oxygen, which of the following does not occur?


6. Redox reactions involve:


7. Nelson’s cell is used to prepare caustic soda along with gases. Which of the following gas is produced at cathode?


8. Pure water is a:


9. In galvanic cell, cathode electrode carries:    


10. In which cell electrical energy is converted into chemical energy?


11. Electrolyte used in silver plating is:


12. Reduction is:


13. Chemical reactions in which the oxidation state of one or more substances changes are called:


14. During the formation of water from hydrogen and oxygen, which of the following does not occur?       


15. Electricity cannot pass through:


16. The oxidation number of oxygen in OF₂ is:  


17. Addition of electron to a substance is known as:


18. In electrolytic cell, the electrode connected to positive terminal of the battery is called:


19. Which statement is correct about the redox reaction of zinc oxide and carbon?


20. Addition of hydrogen during chemical reaction is called:


21. Which one of the following are good reducing agents?


22. In the process of electroplating, the object to be electroplated is washed with solution of:


23. Which ion is not formed during electrolysis of aqueous sodium chloride?


24. Chlorine atom needs ______ electron(s) to complete its octet.


25. Chlorine atom needs how many electrons to complete its octet?


26. The oxidation number of chromium in K₂Cr₂O₇ is:  


27. Oxidation is Appreciated as:


28. In Daniel cell zinc metal is dipped in:


29. Which cell is used in the manufacturing of sodium metal from fused NaCl?


30. Removal of oxygen from a compound is:


31. Which is not a property of fine silver?


32. Which gas is evolved during the electrolysis of fused sodium chloride?


33. In order to give longer life, the containers of iron are coated by:


34. The shape of iron cathode in Nelson cell is:


35. Which one of the following is an oxidizing agent?   


36. Metallic coating can take place by:


37. Rusting occurs on:     


38. Which of the following is not an electrolyte?


39. Reduction takes place at:


40. Electrolysis of fused sodium chloride produces:


41. Sodium hyposulphite dissolves:


42. For the manufacture of sodium hydroxide, the electrolyte used is:


43. Which of the following is undergoing reduction in the following reaction? 2ZnO + C → 2Zn + CO₂


44. Oxidation involves:    


45. The most common example of corrosion is:


46. In rusting process, Iron is:


47. The process of coating a thin layer of zinc on iron is called:


48. Which medium accelerates the process of rusting?


49. Corrosion of iron is called:    


50. The oxidation number of chlorine in KClO₃ is:


51. Which of the following on the surface of iron provide the sites for rusting to occur? 


52. Example of electrolytic cell is:


53. Addition of oxygen during chemical reaction is called:


54. Stainless steel contains:


55. Oxidizing agent is a substance which:


56. Who invented first electrolytic cell?


57. Formation of water from hydrogen and oxygen is:   


58. Water is the oxidation number of oxygen in water?


59. The oxidation number of oxygen in peroxides is:


60. The oxidation number of sulphur in H₂SO₄ is:


61. Which of the following is not electrolyte?


62. The percentage of silver in sterling silver is: 


63. Which of the following is a weak electrolyte?


64. Which of the following is a good electrolyte?


65. Very successful technique against rusting of iron is:


66. Chemical formula of sodium hyposulphite is:


67. The process that takes place in an electrolytic cell is called:


68. A. Volta was:


69. Oxidation always takes place at:


70. In electrolytic refining of copper, Impure copper acts as:


71. Acetic acid is an example of:


72. Electrolytes are classified into how many groups depending upon their extent of ionization in solution?


73. Which of the following ionizes in small extent in water?


74. Which is produced as a result of Redox reaction?     


75. Tin is usually electroplated on:


76. Sodium atom loses _____ electron(s) to form sodium ion.


77. In neutral molecules, the algebraic sum of the oxidation numbers of all the elements is:


78. In Nelson’s cell, cathode is made up of:


79. The formula of rust is:


80. A process of oxidation is:


81. Chlorine gas is formed when chloride ions are:


82. Spontaneous chemical reactions take place in:


83. Cl₂ gas is formed, when Cl‑ ions are:


84. Which of the following electrolytes produces less ions in water?


85. In the redox reaction between Zn and HCl, the oxidizing agent is:      


86. What is the oxidation state of hydrogen in H₂O?


87. The oxidation number of oxygen is ______ in F_2O.


88. In early nineteenth century photographers produce crude images using papers covered with:      


89. Which of the following is a non-electrolyte?


90. The oxidation number of nitrogen in HNO₃ is:


91. Which one of the following is not an electrolytic cell?


92. What happens to a reducing agent in a redox reaction?


93. In HCl, the oxidation number of hydrogen is:


94. In Nelson cell the iron cathode is internally lined with __________ diaphragm.


95. Which of the following is a common example of silver plating?


96. During electrolysis of sodium chloride in aqueous state, which gas is evolved from the cathode electrode?


97. In ions, the algebraic sum of oxidation number equals the __ on the ion.


98. Which one acts as anode in Down’s cell?


99. The substances which do not ionize in solution and do not allow to pass current through them are called:


100. The oxidation number of all elements in free state is:


101. The oxidation number of hydrogen in metal hydrides is:


102. The oxidation number of Group-I elements is:


103. A process of coating a thin layer of Zn on iron is called:


104. The electrolytes which ionize almost completely in their aqueous solutions are called _______ electrolytes.


105. Which cell is used to prepare caustic soda?              


106. The percentage of any metal in the non-silver portion of sterling is:  


107. Which of the following are good electrolytes?


108. Which of the following is not a corrosion resistant metal?


Short Questions

A reaction between carbon and oxygen involved only addition of oxygen (oxidation), but, it is called a redox reaction. Comment on this.
Aluminium corrodes but do not rust. Why?
An element X has oxidation state 0. What will be its oxidation state when it gains three electrons?
Anode of Downs cell is made of a non-metal, what is its name? What is the function of this anode?
Are anodes of Downs cell and Nelson cell made of same element? If yes, what is its name?
Calculate Oxidation number of Cr in K₂Cr₂O₇.
Calculate Oxidation number of Cr in K₂CrO₄.
Calculate oxidation number of Fe in K₄[Fe(CN)₆]
Calculate the oxidation number of chlorine in KClO₃.
The oxidation number of K = +1 and that of O = ⁻².
Calculate the oxidation number of sulphur in H₂SO₄, when O. N. of H = + l and O.N. of O = ⁻².
Define alloy.
Define corrosion.
Define electrochemistry.
Define electroplating.
Define oxidation in terms of electrons. Give an example. 
Define oxidation. 
Define reduction in terms of electrons.
Define reduction in terms of electrons? Give an example.
Define reduction in terms of loss or gain of oxygen or hydrogen. Give an example.
Define reduction.
Define the two types of electrochemical cells and give examples.
Differentiate between a strong and weak electrolyte. Give an example of each.
Differentiate between Cathode and Anode.
Differentiate between Electrolytic and Galvanic cell
Differentiate between Oxidation and Reduction
Differentiate between Oxidizing and reducing agents.
Differentiate between spontaneous and non-spontaneous reactions.
Differentiate between valency and oxidation state (any two).
Does non-electrolytes forms ions in solution?
Explain the role of O₂ in rusting?
Find out the oxidation numbers of N in Cu(NO₃)₂.
Find oxidation number of nitrogen in HNO₃ when the oxidation numbers of H = +1 and O =-2.
Give overall reaction for the preparation of sodium hydroxide.
How can you prove with an example that conversion of anion to an atom is an oxidation process?
How does an electrolytic cell work?
How does galvanizing process take place?
How electroplating of zinc is carried out?
How is electroplating of tin on steel carried out?
How the half-cells of a galvanic cell are connected? What is function of salt bridge?
If the oxidation state of an element changes from +5 to -3. Has it been reduced or oxidized? How many electrons are involved in this process?
In a compound MX₃, find out the oxidation number of M and X.
In electroplating of chromium, which salt is used as an electrolyte?
In electroplating of silver, from where Ag+ ions come and where they deposit?
In H₂S, SO₂ and H₂SO₄ the sulphur atom has different oxidation number. Find out the oxidation number of sulphur in each compound.
In the electrolysis of water, where is the oxygen produced?
Justify that the reaction between ZnO and C is Redox reaction.
Name different types of electrochemical cells.
Name the by-products produced in Nelson’s Cell.
Oxidation and reduction proceed simultaneously. Explain, with an example.
Rusting completes in how many redox reactions?
What are cathode and anode in the process of silver electroplating?
What are electrolytes? Give any two examples.
What are non-Electrolytes?
What are non-Spontaneous reactions?
What are oxidizing and reducing agents?
What are spontaneous reactions?
What do you mean by galvanizing and what is the advantage of galvanizing?
What happens at the cathode in a galvanic cell?
What happens to iron in the rusting process?
What happens to oxidation number after oxidation and reduction?
What is a redox reaction?
What is brine?
What is corrosion?
What is difference between a strong electrolyte and a weak electrolyte?
What is electrolysis?
What is half cell?
What is meant by electrochemical cell?
What is meant by electrochemistry?
What is meant by electrolytic cell?
What is meant by galvanic cell?
What is meant by oxidation state or oxidation number? Give an example.
What is meant by Oxidation State?
What is meant by oxidation?
What is meant by Redox?
What is meant by rust?
What is meant by salt bridge?
What is meant by stainless steel?
What is the advantage of galvanizing?
What is the difference between corrosion and rusting?
What is the important condition for rusting?
What is the name of the by-product produced in the Downs cell?
What is the nature of electrode used in electroplating of chromium?
What is the oxidation number of an element in its free state?
What is the oxidation number of elements of group 1, group 2 and group 13?
What is the principle of electroplating?
What is the purpose of electroplating?
What is the shape of cathode in Nelson’s cell? Why is it perforated?
Where do the electrons flow from Zn electrode in Daniel’s Cell?
Where does the sodium metal is collected in Downs cell?
Which by-products are produced during the manufacture of NaOH from brine? 
Which ions are discharged at cathode in Nelson’s cell and what is produced at cathode?
Which is the best method to prevent corrosion and which metals are used for this?
Which material is used to make cathode in electroplating?
Which solution is used as an electrolyte in Nelson’s Cell?
Why an iron grill is painted frequently?
Why anode is made of carbon (graphite) during the electrolysis of sodium chloride?
Why are the strong electrolytes termed as good conductors?
Why do electrodes get their names ‘anode’ and ‘cathode’ in galvanic cell?
Why does the anode carry negative charge in galvanic cell but positive charge in electrolytic cell? Justify with comments.
Why does the process of rusting only occur on iron and not on the surface of aluminium?
Why electricity cannot pass through solid NaCl?
Why few drops of an acid are added in water during its electrolysis?
Why is galvanizing done?
Why is O₂ necessary for rusting?
Why is steel plated with nickel before the electroplating of chromium?
Why is the anode made up of a metal to be deposited during electrolysis?
Why non-metals are oxidizing agents while metals are reducing agents?
Why the oxidation number of oxygen in OF₂ is +2?
Why the positively charged electrode is called anode in electrolytic cell?
Why tin plated iron is rusted rapidly when tin layer is broken?
Write applications of galvanic cell.
Write construction of an electrolytic cell.
Write construction of Down’s cell.
Write oxidation numbers of oxygen in its binary compounds.
Write the reactions taking place during electrolysis of the molten Sodium Chloride. 
Write the redox reaction taking place during the electroplating of chromium. 


Long Questions


Compare electrolytic and galvanic cell.
Define corrosion and rusting. Describe any three methods for prevention of corrosion.
Define electrolyte. Discuss its different types.
Define electroplating and describe electroplating of Zinc and Tin.
Define oxidation state. Write the rules for assigning oxidation number.
Describe electroplating of Chromium in detail.
Describe in details the electrolysis of fused NaCl in Downs cell.
Describe the rules for assigning the oxidation state
Differentiate between electrolytes and non-electrolytes with examples.
Differentiate between oxidizing and reducing agents with the help of an example.
Discuss manufacturing of NaOH by Nelson’s cell in details.
Discuss the construction and working of a cell in which electricity is produced.
Discuss the electrolysis of water.
Discuss the redox reaction taking place in the rusting of iron in detail.
Discuss, why galvanizing is considered better than that of tin plating.
Explain oxidation and reduction in terms of loss and gain of electron.
Explain physical methods of metallic coating.
Explain redox reactions with the help of two examples.
Explain the manufacturing of sodium metal from fused NaCl.
Explain the process of rusting of iron.
How can a non-spontaneous reaction be carried out in an electrolytic cell? Discuss in detail.
How can we prepare NaOH on commercial scale? Discuss its chemistry along with the diagram.
How electrolytic refining of copper is carried out?
How NaOH is manufactured from Brine? Explain.
State the work and construction of Daniel cell.
What is corrosion? Write four methods for prevention of corrosion.
What is electrolytic cell? Explain its working.
What is electroplating? Describe the procedure of electroplating.
What is the principle of electroplating? How electroplating of chromium is carried out?
Write a note electrolysis of water.

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