Chapter 7 (Part 2)|9th class Chemistry|tutoronlines

Chapter No 7 (part 2)

Electrochemistry

Table of content:

Sr . No Name of element
1 Electrochemistry
2 Reducing agent
3 Oxidizing agent
4 Electrolytic cell
5 Non electrolytes
6 Galvanic cell
7 Electrolysis
8 Nelson’s Cell
9 Anode
10 Reducing agent
11 Oxidizing agent
12 Electrolytic cell
13 Galvanizing
14 Non Electrolytic
15 Galvanic cell
16 Electroplating
17 Cathode
18 corrosion
19 Electro chemical cell
20 Electrolysis

Give short Answer to the following Questions

Q.No.15. Calculate the oxidation number of Mn of KMnO4?

Ans. ( oxidation number of K ) + (oxidation number of Mn) + 4 (oxidation number of O) = 0
1+Mn+4(-2) = 0
1+ Mn – 8 =0
Mn = 8-1
Mn = 7

Q.No.16. Define reducing agent also give one example?

Ans. Those species which reduce other substance and themselves get oxidization is know as reducing agent. e.g All metals are good reducing agent.

Q.No.17. Differentiate between oxidizing and reducing agents?
Ans. Oxidizing agent:

The type of specie that oxidize the substance by taking electron form it and themselves get reduced by gaining the electron e.g. non metals are oxidizing agents.

Reducing agent:

The type of specie that reduce other substance by giving them electron and themselves get oxidize. Almost all metal are good reducing agents, because they have tendency to lose electrons.

Q.No.18. Which substance is oxidized and reduced in following reaction. Identify these ?

Ans. In this reaction sodium get oxidize which chlorine become reduce.

Q.No.19. Define electrolytic cell?

Ans. The type of electrochemical cell in which a non spontaneous chemical reaction take place when electric current is passed through solution is called electrolytic cell.

Q.No.20. Differentiate between strong and weak electrolytes?

Ans. Strong electrolytes ionize completely in an aqueous solution. NaCl, NaOH and H2SO4 are example. Weak electrolytes ionize completely in an aqueous solution CH3COOH and Ca(OH) are examples.

Q.No.21. Explain Non electrolytes with an example?

Ans. Those species that do not ionize in an aqueous solution and current is not passing through their solution is called non electrolytes e.g. sugar solution.

Q.No.22. What is the difference between electrolytic cell and galvanic cell?
Ans. Electrolytic cell:

It consist of complete cell which is connected with battery.
Anode has positive while cathode has negative charge.
Electrical energy is converted into chemical energy.
Current is used for non spontaneous chemical reaction.

Galvanic cell:

It consist of two half cells.
Anode has negative while cathode has positive charge.
Chemical energy is converted into electrical energy.
Redox reaction take place by its own.

Q.No.23. What is salt bridge? What is its basic function?

Ans. The half cells of galvanic are connected by salt bridge. It provide pathway for migration of ions. And keep the solution neutral.

Q.No.24. What is meant by electrolysis?

Ans. When an electric current is passing through a aqueous solution or melted form of a compound it decomposes into its basic component this process is known as electrolysis.

Q.No.25. What is electrochemical cell? Write the name of its types?

Ans. A type of cell in which two electrodes are immersed in electrolyte solution and both are connected with battery.
There are two type of electrochemical cell.
Electrolytic cell, Galvanic cell.

Q.No.26. What happens at the cathode in a Galvanic cell?

Ans. In Galvanic cell reduction has been done.

Q.No.27. Name the By produced in Nelson’s Cell?

Ans. In Nelson’s Cell, two by products hydrogen and chlorine are formed.

Q.No.28. Where do the electron flow from Zn electrode in Daniel’s Cell?

Ans. In Daniel’s Cell electrons accumulate on zinc electrode which moves toward cathode through external cricuit.

Q.No.29. Write the names of Electro chemical cells?

Ans. There are two types of Electrochemical cell.
(i) Electrolytic cell
(ii) Galvanic cell.

Q.No.30. What is the difference between Anode and cathode?

Ans. That electrode which is connected to positive terminal known as anode. That electrode which is connected to negative terminal is known as cathode.

Q.No.31. How the half cell of galvanic cell are connected? What is the function of salt bridge?

Ans. The half cell are connected through salt bridge. The bride provide the pathway for for migration of ion is solution.

Q.No.32. Are anodes of Downs cell and Nelson cell made of the same element? If yes write its name.

Ans. Yes the anodes of Downs cell and Nelson cell are made of the same element graphite.

Q.No.33. Define Galvanic cell and give one example?

Ans. That type of electrochemical cell in which spontaneous chemical reaction take place and current is produced. e.g Daniel cell.

Q.No.34. Define electrolytes also given one example?

Ans. Those substance which allow to pass electricity through their solution or molten form is known as electrolyte.
e.g. Solution of acid, bases and salts are good electrolytes.

Q.No.35. Why galvanizing is done?

Ans. To prevent from rust, iron is being galvanized.

Q.No.36. What is meant by alloying?

Ans. The homogenous mixture of metal with other metal or non metal is called alloying. Alloying of iron with other metal prove to be successful technique against rust pollution. The good example of its steal less steal. Which is mixture of iron, chromium and nickel.

Q.No.37. Define metallic coating. In which industry it is used much?

Ans. The best method to prevent metals from being rusting is metallic coating. Tin, zinc and chromium are used in coating. this technique is commonly used in food industry. Where food is preserved in boxes these iron boxes are coated with tin or chromium.

Q.No.38. Define electroplating?

Ans. The layering of one metal to another through electrolysis is called electroplating.

Q.No.39. Define corrosion with an example?

Ans. It is slow and continuous process of eating away of a metal by the surrounding medium. It is redox reaction that take place by the action of air and moisture with metals.

Q.No.40. What do you mean by rusting of iron?

Ans. A slow and continuous process of eating away of metal by its surrounding called rusting of iron.

Q.No.41. Why O2 is necessary for rusting?

Ans. Because oxygen act as oxidizing agent. It accept electron from iron and change it into ferrous ion and then ferric ion. Oxygen combine with ferrous ion in the presence of water and from rust (Fe2O3.nH2O).

Q.No.42. Why an iron grill is painted frequently?

Ans. In order to prevent from rusting, the iron grill painted frequently. Because due to moisture in air it is at risk of being rusted.

Q.No.43. How electroplating of Tin on steel is carried out?

Ans. Tin is usually electroplated on steel by placing the steel into a container containing a solution of tin salt. The steel is connected to a electrical circuit, acting as cathode. While other electrode made of tin metal act as anode. When an electrical current passes through circuit tin metal ion present in solution deposit on steel.

Q.No.44. What is the shape of cathode in Nelson’s cell? Why is it perforated?

Ans. In Nelson cell cathode contain a perforated tank. It is perforated because sodium hydroxide solution has to percolates into catch basin.

Q.No.45. How Impure copper is refined to pure copper?

Ans. Copper is refined through electrolytic process impure copper act as anode and pure copper act as cathode. The solution of copper sulphateact as electrolyte.
The oxidation is carried out on andoe. Impure copper gives electrons to anode and dissolves in solution as copper ion.
The process of reduction is carried on cathode. copper ion attract toward cathode and attain electron from cathode.

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