9th chemistry chapter 7 solved exercise short questions


9th chemistry chapter 7 solved exercise short questions

Q#1 : Define oxidation in terms of electrons . Give an example .

Oxidation :

” Oxidation is the loss of electrons by an atom or an ion “

Example :

Q#2 : Define reduction in terms of loss or gain of oxygen or hydrogen . Give an example .

Reduction :

” The addition of hydrogen or removal of oxygen during a chemical reaction is called reduction “

Example :

Q#3 : What is difference between valency and oxidation state ?

Q#4 : Differentiate between oxidizing and reducing agents .

Q#5 : Differentiate between strong and weak electrolytes .

Q#6 : How is electroplating of tin on steel carried out ?

Electroplating of tin :

Tin is usually electroplated on steel by placing the steel into a container containing a solution of tin salt .

The steel is connected to an electrical circuit , acting as cathode .

→While the other electrode made of tin metal acts as anode .

When an electrical current passes through the circuit , tin metal ion present in the solution deposit on steel .

Q#7 : Why is steel plated with nickel before the electroplating of chromium .

Steel is steel plated with nickel before the electroplating of chromium .

Reason :

Because chromium do not adhere well on the steel surface . and

chromium allows moisture to pass through it and metal is stripped off .

That’s why before chromium plating , nickel is plated first on steel .

Q#8 : How can you explain that following reaction is oxidation in terms of increase of oxidation number ?

” The loss of electron is called oxidation .

Al⁰ → Al³+ + 3e-

In above equation :

Al⁰ with zero oxidation state changes to Al³+ by loss of 3 electrons .

So, oxidation reaction takes place .

Q#9 : How can you prove with an example that conversion of an ion to an atom is an oxidation process ?

Example :

  • In this equation , loss of electrons take place .
  • Chlorine Ion (anion ) converts into chlorine molecule by losing electrons .
  • So, oxidation takes place .

Q#10 : Why does the anode carry negative charge in galvanic cell but positive charge in electrolytic cell ? Justify with comments .

  • In case of Galvanic cell , electrons are lost by the atoms at anode plate and make it electron rich .

So, anode carry negative charge .

  • In case of Electrolytic cell , the anode is attracted to the positive terminal of the battery .

That is why , it carry positive charge .

Q#11 : Where do the electrons flow from Zn electrode in Daniel’s cell ?

In Daniel cell , the electrons flow from Zn electrode (anode) towards the cathode made up of copper .

Q#12 : Why do electrodes get their names ‘anode’ and cathode in galvanic cell ?

  • In Galvanic cell;

Where oxidation takes place is referred as anode .

While where reduction takes place is referred as cathode .

Q#13 : What happens at the cathode in a galvanic cell ?

The galvanic cell , reduction of Cu+2 ions takes place at cathode .

The electrons are gained by “Cu” ions of solution and “Cu” atoms are deposited at cathode .

Cu+2 + 2e- → Cu0

Q#14 : Which solution is used as an electrolyte in Nelson’s cell ?

In Nelson’s cell, Brine (saturated solution of NaCl) is used as an electrolyte .

Q#15 :Name the by-products produced in Nelson’s cell ?

By-products produced in Nelson’s cell are :

  • Hydrogen gas (H2 )
  • Chlorine gas (Cl2 )

Q#16 : Why galvanizing is done ?

Galvanizing is done to protect the iron against corrosion . It protects iron even after damage to zinc layer .

” The process of coating a thin layer of zinc or iron is galvanizing .”

Q#17 : Why is an iron grill painted frequently ?

Iron grill is painted frequently .

Reason :

Because , due to presence of oxygen and water in air , it may corrode .

Iron is painted , to prevent from rusting.

Q#18 : Why is O2 necessary for rusting ?

Oxygen acts as an oxidizing agent in rusting and oxidizes iron by gaining electrons from it in presence of H+ ions .

O2 + 4H+ + 4e → 2H2O

Q#19 : In electroplating of Chromium , which salt is usd as an electrolyte ?

Chromium sulphate Cr2(SO4)3 with few drops of H2SO4 acts as an electrolyte in electroplating of chromium.

Q#20 : Write three redox reaction taking place during the electroplating of chromium ?

Redox reaction :

Cr2(SO4)3 → 2Cr+3 + 3SO-24

Oxidation at anode :

4OH → 2H2O + O2 + 4e

Reduction at cathode :

Cr+3 + 3e → Cr

Q#21 : In electroplating of silver , from where do Ag+ ions come and where do they deposit ?

In electroplating of silver , Ag+ ions come from anode made up of pure silver and they deposit at cathode .

At anode :

Ag → Ag+ + e

Ag+ + e → Ag

Q#22 : What is the nature of electrode used in electroplating of chromium ?

  • Anode is made up of antimonial lead while
  • Cathode is made up of the object to be electroplated .

#9th_class_chemistry_chapter_7_part_2 #9th_class_chemistry_chapter_7 #9th_class_chemistry #Electrochemistry #Matric_part_1_chemistry_chapter_7 #9th_chemistry_chapter_7_in_Hindi #9th_chemistry_chapter_7_in_Urdu #Online_lecture_of_chemistry_9th_class #Online_chemistry_lecture_9th_class

1 thought on “9th chemistry chapter 7 solved exercise short questions”

  1. Pingback: 9th chemistry chapter 7 solved exercise MCQs - learn with ZahraAwan

Leave a Comment

Your email address will not be published. Required fields are marked *