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Chemistry Chapters

9th Class Chapter 7 Chemistry Long Questions

Dear students, prepare for chemistry class 9th chapter 7 long questions. These important long questions are carefully added to get you best preparation for your 9th class chemistry ch. 7 exams.
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Question: 1
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859981842552128730179">:</gwmw>5<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859981842550304202928">(</gwmw>A) How sodium metal is extracted from fused sodiumchloride in Down's cell?
Answer: 1
1-20
On the industrial scale molten Sodium metal is obtained by the electrolysis of fused NaCl is the Downs cell. This electrolytic cell is a circular furnace. In the center there is a large block of graphite, which acts as an anode cathode round it is made of iron
Working of Downs cell:
The fused NaCl produces Na+ and Cl-inon, which migrate to their respective electrode on the passage of electric current.Nollen Nacl ionizes as
2NaCl = 2 Na+ +2Cl-
reactionat cathode
2Na+ + 2e- _____> 2Na
Overall galvanic reaction
2NaCl ______> Cl2 +2Na
Question: 2
Q no (B) Explain oxidation-reduction reaction with suitable examples.<div><br></div>
Answer: 2
2-20
Oxidation is defined as addition of oxygen or removal of hydrogen during a chemical reaction .Reduction is defined as additionof hydrogen or removal of oxygen during a chemical reaction. Both of these process take place simultaneouslyin a reaction we can say where there is oxidation there is reduction
Removal of oxygen.
2Zn0 + C _____> 2Zn + Co2
Addition of oxygen.

Question: 3
Q no: 6 (A) How can prepare NaOH on <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15860000858221225216840">commercial scale</gwmw>? Discuss its chemistry along with diagr<gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859994741870753391248">am</gwmw><gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859994741873386857420">?</gwmw> How sodium hydroxide is manufactured brine solution in Nelson's cell?
Answer: 3
3-20
Corrosion is a general term but corrosion of iron is called rusting. The important condition for rusting is moist there will be no rusting in water vapourfree of air or air free of water.
Now we study the chemistry of the rusting process stains and dentson the surface of the iron provide, the sites for this process to occur. This region is called anodic region and following oxidation reaction take place here.
2 Fe ______>2Fe+² +2 +4e-
This loss of electrons damage the object. The free electrons move through iron sheet, until they reach to a region of relatively high O2
O2 +4H+ + 4e- ________>2H2O.

The overall reaction process is completed without the fomation of rust

2Fe+O2 + 4H ______> 2Fe+2 + 2H2O

2Fe+2 + ½ O2 + (2+n) H2o ____> Fe2O3.nH2O+4H2

Question: 4
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15860021008106498754465">:</gwmw>6 (B) Describe the rules for assigning oxidation state.
Answer: 4
4-20
The oxidation number of all elements in the free state is zero,
The oxidation number of an ion consisting ofa single element is the same as the charge on the ion.
The oxidation number of different elements in the periodic table, in Group 1 is +1 , in Group 2 it is +2 and it Group B it is +3
The oxidation number of hydrogen in all it,s compound is +1 But in metal hydrides it is -1
The oxidation number of oxygen in all it,s compound is -2. But it is -1 in peroxide and _2 inOF2.
Question: 5
Q no: 7 (A) What is meant by Galvanic cell? Write construction and working of Daniel cell.
Answer: 5
5-20
Galvanic cell:
The electrochemical cell in which a spontaneous chemical reaction takes place and generates electric current is called galvanic or voltaic cell.
Construction of a Daniel cell:
A galvanic cell consists of two cells each called as half cell connected electrically by a salt-bridge. In each of the half-cell, an electrode in dipped in 1M solution it's own salt and connected through a wire to an external circuit hypicalgalvanic cell
Working of the cell
The Zn metal has tendency to lose electrons more readily than copper Half cell reaction at anode
Zn ____> Zn+2 + 2e-

Half cell reaction at cathode
Cu+2+ 2e _____> Cu
Overall galvanic reaction
Zn + Cu+2______> Zn+2+Cu
Question: 6
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15861509345188467563383">(</gwmw>B) Describe the electroplating of chromium in detail.
Answer: 6
6-20
The electroplating of is out in the same way as that of silver The object to be electroplated is dipped in of a little acid acts as electrolyte. The object to be electroplated acts as cathode while anode is made of lead The electrolyte ionizes and provides Cr3+ions
Electrolyle produces the following ions
Cr2 (So4) ______> 2cr+3 + 3SO4-2
Reactions at the electrodes are following At anode e40H- ____> 2 H20 + O2 +4e-
At cathode Cr+3 + 3e- _____>Cr
For parctialconveniencethe steel or copper and then by chromium because it does not othere well on the on the steel surface
Question: 7
Write a note on oxidation and reduction reactions.
Answer: 7
7-20
Based of oxidation and reduction; one concept of oxidation and reduction is based upon either addition or removal of oxygen or addition or removal of hydrogen in a chemical reaction.
Oxidation: oxidation is defined as addition of oxygen or removal of hydrogen during a chemical reaction
Reduction: reduction is defined as addition of hydrogen or removal of oxygen during a chemical reaction
Result: both of these process take place simultaneously in a reaction , we can say
"where there ix oxidation there is reduction".
Question: 8
Define and explain oxidation and reduction in terms of loss or gain of electron
Answer: 8
8-20
Definition: reactions which involve loss or gain of electros are called oxidation and reduction reactions.
Question: 9
Write a complete note on electrolytic cells
Answer: 9
9-20
Definition: the type of electrochemical cell in which a non-spontaneous chemical reaction takes place when electric current is passed through the solution is called an electrolytic cell.
Question: 10
What do you know about electrochemical cells and concept of electrolytes?
Answer: 10
10-20
Electrochemical:
Definition: electrochemical cell is a system in which two electrodes are dipped in the solution of an electrolyte which is connected to the battery.
Question: 11
Describe electrolysis of water?
Answer: 11
11-20
pure water is a weak electrolyte. It ionizes to a very small extent. The concentrations of hydrogen ion(H+) and hydroxyl ions(OH-) are both at 10-7 mol of dm-3 respectively. When a few drops of an acid are added in water, its conductivity improves.When an electric current is passed through this acidified water, Oh- anions move toward positive electrode( anode ) and H+ cations move toward negative electrode(cathode) and discharge takes place at these electrodes.They produces oxygen and hydrogen gases respectively at anode and cathode.The redox reaction takin place in he electrolytic bath.
Question: 12
Write a note on galvanic cell also explain its working also.
Answer: 12
12-20
Definition: the electrochemical cell in which a spontaneous chemical reaction takes place and generate electric current called galvanic cell or voltaic cell.Example; examples of these type of cell is a Daniel cell.
Question: 13
describe the manufacturing of sodium metal from fused NaCl.
Answer: 13
13-20
On the industrial scale molten sodium metal is obtained by the electrolysis of fused NaCl in the Downs cell. This electrolytic cell is a circular furnace. In the center there is a large block of graphite which acts as an anode while cathode around it is made of iron.
Question: 14
Explain the manufacturing of NaOH from brine.
Answer: 14
14-20
Manufacturing of NaOH from Brine:
on industrial scale caustic soda, sodium hydroxide NaOH, is produced in Nelson's cell by the electrolysis of the aqueous solution of NaCl called brine.

Question: 15
Write note on corrosion.
Answer: 15
15-20
Corrosion: corrosion is a slow and continuous eating away of a metal by the surrounding medium. It is a redox chemical reaction that takes place by the action of air and moisture with the metals.Example: the most common example of corrosion is rusting of iron.
Question: 16
Does aluminum rust?
Answer: 16
16-20
Al corrodes but it does not rust . Rust refers only to iron and steel-corrosion. A very hard material Al oxide protects aluminum from further corrasion. In comparison to that when iron corrodes, its color changes and produces large red flakes know as rust. Unlike aluminum oxide, the expanding and flaking of rust exposes new metal surface to further rusting.
Question: 17
Write detail note on the prevention of corrosion?
Answer: 17
17-20
Prevention of Corrosion :
Removal of stain: the region of stains in an iron rod act as the site for corrosion. If the surface of iron is properly cleaned and stains are removed, it would prevent corrosion.
Question: 18
Difference between electrolytic and galvanic cell.
Answer: 18
18-20
Galvanic cell:
  • It consist of two half-cells connected through a salt bridge.
  • Anode has negative charge while cathode has positive charge.
  • Chemical energy is converts into electrical energy.
  • Redox reaction takes place spontaneously and produce electric current.
Question: 19
Write a note on electrolytic refining of copper.
Answer: 19
19-20
Electrolytic Refining of copper: Impure copper is refined by the electrolytic method in the electrolytic cell. Impure copper acts as anadem and a pure copper plate acts as cathode. Copper sulphate solution in water is used an an anode and a pure copper plate acts as a cathode. Copper sulphate solution in water is used as an electrolyte.
Question: 20
Describe electrolytic methods of prevention from corrosion.
Answer: 20
20-20
Electroplating: electroplating is depositing of one metal over the others by means of electrolysis.Explanation: this process is used to protect metals against corrosion and to improve their appearance. Principle of electroplating is to establish an electrolytic cell in which anode is made of metal to be deposited and cathode is of the object on which metal is to deposit. The electrolyte is in aqueous solution of a salt of the respective metal.