Chemical effects of electric current- class 8 Important Questions

-

Chapter- Chemical Effect of Electric Current

Part- A 

Q1. What is an electdt ftrode?

Ans. An electrode is a conductor which is in contact with the electrolyte.

 Q2. What is an ion?

Ans. The atom which becomes charged by losing or gaining one or more electrons is called an ion.

Q3. Mercury is a liquid that conducts electricity, which constitutes a current through it?

Ans. In mercury, a current is constituted by the flow of free electrons.

Q4. Why is an acid or an ionic salt added to water in the electrolysis of water? 

Ans. Because the ions of the ionic compound will increase the conductivity of water.

Q5. A metal is released in the electrolysis is of salt at what electrode will it be deposited?

Ans. In the electrolysis of salt, all the metals are deposited at the cathode (negative terminal).

Part- B

Q1. Why are metals good conductors of electricity?

Ans. Some of the electrons in the metals are not tightly packed in the metal. When no battery is applied these electrons are moving in all directions but when a battery is applied across the conductor. All electrons start moving in one direction.

Q2. What are electrolytes? Give examples.

Ans. When an ionic compound is dissolved in the water then this compound splits into its ions. This liquid paste of these ions is called the electrolyte. For example, NaCl solution, KI solution.

Q3. What happens when a voltage is applied across electrode placed in an electrolyte?

Ans. In the electrolyte, ions are free to move in all directions. But when voltage is applied, all the ions will move towards the negative electrode (cathode) and negative ions move towards the positive electrode (anode). This movement of ions will make the current in the electrolyte.



 

Part-C

Q1. Explain electrolysis. What happens in the electrolysis of water?

Ans. Electrolysis.  In this process, electrolyte breakdown into its constituent ions when electricity is passed through it is called electrolysis.

            When current is passed through water, it divides into H+ and OH- ions. H+ ions will negative terminal and OH- ions move towards the positive terminal. At the terminals, they will form H2 (at Cathode) and O2 (at the anode) gas.


2H2O           à                          2H2         +             O2

                Electricity,         At Cathode              At anode.

 

Q2. Write the uses of electrolysis.

Ans.1. It is used for making of chlorine gas.

2 it is used for the purification of metals.

3   it is used for the electroplating of utensils.

4 it is used in the extraction of metals from ores.

5 it is used for making H2 gas and O2 gas.

 Q3. What is electroplating? How are steel spoons plated with silver?

Ans. Electroplating. The process of coating a costly metal on cheap metals is called electroplating.

In the electroplating of a spoon, both silver rod and spoon in the silver salt solution, the silver rod is connected with the positive terminal of the battery and spoon is connected negative terminal of the battery. Silver ions (Ag+) will move towards the negative electrode (spoon) and it will be deposited on the spoon.

Prepared By - Anmol


 


Comments

Post a Comment

Popular posts from this blog

Metals and non - metals

-
PART-A Q1: name any ten metals. Ans :iron, copper, aluminium, sodium copper, silver, magnesium, gold, Mercury ,calcium. Q2: metals have high tensile strength, explain. Also give one example of how this property of metals is used. Ans: metals are very strong. It cannot be broken easily. Steel cables are used to carry heavy loads. Q3: why can't you (A) draw wires from a piece of wood or coal . Ans: because wood or coal are brittle and not flexible. (B) use nylon or jute ropes for  electrical transmission? Ans: no, because these are bad conductor of electricity. (C) use a cooking utensils made of cardboard. Ans: because , cardboard is a bad conductor of heat. It will not give heat in all direction. Q4: name five metals which are gaseous at ordinary temperature?  Ans: hydrogen coma oxygen nitrogen , neon,  chlorine. Q5:name two metals which react vigorously with cold water. Name one metal which, if ignited, continuous to burn in stream? Ans: sodium and potassium can react ...
Read more

Pollution of air and water

-
PART- A Q1: what do you mean by polluted air or water? Ans: if your water contains some substances that are harmful for us and our environment, then that air or water is said to polluted air or water. Q2: mention any three observation that indicate that a given sample of water is polluted? Ans: 1   its colour is dirty. 2 It tastes bad. 3 It is smells bad. 4 Oral oil grease is float in . Q3: what is chemical  pollution of water? Ans: if harmful chemicals mix with water bodies , then it cause chemical pollution of water. Q4: name the six chemical pollutants  of water. Ans: 1   oil and grease  2  Mineral acids 3  Pesticides and fertilizers 4  Metals and their compounds 5  Synthetic chemicals 6  Phosphate  from detergents. Q5: name four water- borne  diseases? Ans: typhoid Cholera Dysentery Hepatitis. Q6: what do you mean by portable water? Ans: the water which is good for drinking is called portable water. Q7 : how is ac...
Read more

Class 9 Animal Tissue

-
Image
Animal tissue There are several types of animal tissues and these are often grouped together into the four main classes that for many classes are the following:- Every category is further subdivided into different subcategories, that we will discuss later in this article:- 1. Epithelial Tissue :- It is arranged in single or multi-layered sheets. It covers the internal and external surface of the body.Epithelial tissue is not supplied by the blood vessels. It  is classified following into the further sub 5 categories according to the distributions:- A)  Squamous Epithelium:- I ts cells are thin, flat with clear cytoplasm. A single round nucleus is present in the centre.It  is found in the kidney tubules, bowman capsule etc.  B)  Cuboidal Epithelium :- Cells of this Epithelium a long, broad in shape and they appear like a cube. The cytoplasm is also present in this with centrally located nucleus. It is found in the kidney tubules, ducts of the slavery ...
Read more