Solution of Chapter 14. Chemical Effects of Electric Current (Lakhmir Singh & Manjit Kaur - Science Book)

Do liquids also conduct electricity?

Name two liquids which conduct electricity and two liquids which do not conduct electricity.

Name a device which glows even when a weak electric current passes through it.

Write the full form of LED.

How would you classify lemon juice- a good conductor or a poor conductor of electricity?

Vinegar is a sour liquid. State whether vinegar will conduct electricity or not.

What effect does an electric current produce when flowing through a conducting liquid (or conducting solution)?

When electric current is passed through acidified water, then hydrogen and oxygen are formed. What type of effect of current is illustrated by this statement?

Acidified water is electrolyzed by using carbon electrodes. What is produced at:

(a) positive carbon electrode?

(b) negative carbon electrode?

Give one example of the chemical effect of electric current.

What should be done to decompose water into hydrogen and oxygen?

Name the process in which a coating of one metal can be deposited on the surface of another metal by using current from a battery.

Name the metal which is usually electroplated on car parts such as bumpers and bicycle handlebars made of steel.

Which metal is electroplated on iron for making 'cans' used for storing food?

Name two metal objects which have a coating of another metal.

Name the most common application of the chemical effect of electric current.

Name two metals which are usually electroplated on cheaper metals for making jewelry (or ornaments).

Which is the polluting waste generated by electroplating factories?

Give a list of five objects around you which are electroplated.

Name two metals which are purified by using the chemical effect of current (or electrolysis).

Name two metals which are produced (or extracted) by using the chemical effect of electric current.

Name one chemical compound which is produced by using the chemical effect of electric current.

Name one compound which is decomposed into hydrogen and oxygen by using the chemical effect of electric current.

State whether the following statements are true or false :

(a) Rainwater is a non-conductor of electricity.

(b) A piece of fresh potato does not conduct electricity at all.

Fill in the following blanks with suitable words:

(a) Most liquids that conduct electricity are solutions of ..........., ......... and ............

(b) LED glows even when a ..............electric current passes through it.

(c) The passage of an electric current through a conducting solution causes.............effect.

(d) When electric current is passed through acidified water, then ........and...........are formed.

(e) The process of depositing a layer of any desired metal on another metal by means of electricity is called ..........

(f) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ............terminal of the battery.

Which of the following liquids conduct electricity and which do not conduct electricity?

Lemon juice, Milk, Vinegar, Common salt solution, Sulphuric acid solution, Sugar solution, Distilled water, Honey, Sea water, Rainwater.

Why is it dangerous to touch a working electrical appliance with wet hands?

What is the advantage of using LED in testing the electrical conductivity of liquids ?

Which effect of electric current is utilized for detecting the flow of current through a solution:

(a) when a torch bulb is used?

(b) when a compass is used?

What happens to the needle of a compass kept nearby when electric current is switched on in a wire? Why does this happen?

Explain why, distilled water does not conduct electricity but tap water conducts some electricity.

Distilled water does not conduct electricity. What substances can be added to distilled .water in small amounts to make it a good conductor of electricity? Why?

Which of the two is a better conductor of electricity: drinking water (tap water) or sea water? Give reason for your answer.

Why does a brand new bicycle have shining handlebar and wheel rims? What will happen if these are accidently scratched?

Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.

When the free ends of a conductivity tester (made by using a battery connected to a wire wound around a compass) are dipped into a solution, the magnetic needle shows deflection. Can you give the reason for this deflection.

A beaker contains an acidified copper sulphate solution. A copper plate and a carbon rod are kept in this copper sulphate solution. The copper plate is connected to the positive terminal of a battery whereas the carbon rod is connected to the negative terminal of the battery. What will you observe when an electric current is passed through this set-up for a considerable time?

Does pure water conduct electricity? If not, what can we do to make it conducting?

In case of a fire, before the firemen use the water hoses to throw water to douse fire, they shut off the electricity supply for the area. Explain why this is done.

Which effect of electric current is utilized when a thin layer of chromium metal is deposited on an iron tap? What is this process known as?

For electroplating copper on an iron object, which terminal of the battery (positive or negative) is connected to the iron object? Also name the electrolyte you will use for this purpose.

What is meant by the chemical effect of electric current? Explain with the help of an example.

Name any two applications of the chemical effect of electric current.

What is electrolysis? Explain why, in the electrolysis of water, 'acidified water' is used.

Name three types of substances in which an electric current can produce a chemical effect.

State some of the characteristics of chemical changes brought about by the chemical effect of electric current.

Why does an electric bulb glow when a current passes through it?

What is meant by electroplating? What is the purpose of electroplating?

Which properties of chromium metal make it suitable for electroplating it on car bumpers, bath taps and bicycle handlebars, etc., made of iron?

A strip of impure copper metal is given to you. Describe briefly how you will purify it by using the chemical effect of electric current. Draw a labelled diagram of the experimental set up used for this purpose.

With the help of a labelled diagram, describe briefly how an iron key can be electroplated with copper.

In an activity to check the conduction of electricity through two liquids labelled A and B by using a bulb, it is observed that the bulb glows brightly for liquid A while it glows very dimly for liquid B.

Which of the following does not conduct electricity?

Which of the following metals should be electroplated on a tiffin box made of steel?

Which of the following metals are produced by the electrolysis of their molten compounds ?

A) Copper

B) Silver

C) Aluminium

D) Sodium

Which of the following types of energy can be used to decompose water into its elements?

Which of the following compounds is manufactured by using the chemical effect of electric current?

Which of the following objects should not be chrome-plated ?

Which of the following is a weak electrolyte ?

Electrolytes conduct electricity due to the movement of:

Non-metals are generally non-conductors of electricity. The non-metal whose one of the forms can be used to make electrodes in electrolysis experiments is:

The decomposition produced by passing current through a conducting liquid is called:

Which of the following is not an application of the chemical effect of electric current?

One of the following is not used for electroplating metal articles. This one is :

An arrangement having two carbon rods kept in a conducting liquid in a vessel is known as:

Which of the following effects is not prodused by the chemical reactions brought about by an electric current?

Which of the following can be electroplated with chromium ?

A) Bakelite B) Graphite

C) Steel D) Teflon

In order to obtain a coating of silver metal on a flower vase made of copper, the electrolyte has to be:

The process of purification of an impure metal is like:

The device which can be used to detect very small current flowing in an electric circuit is:

If plus sign (+) denotes the positive electrode and minus sign (-) denotes the negative electrode, then which of the following statement is correct for an iron spoon to be copper-plated ?

A student staying in a coastal region tests the drinking water and also the sea water 'With a circuit in which a part of the connecting wire is wound around a matchbox containing compass. He finds that the compass needle deflects more in the case of sea water. Can you explain the reason?

When an electric current is passed through a cut potato for a considerable time, a coloured spot is formed around one of the electrodes :

(a) What is the colour of the spot?

(b) Around which electrode (positive or negative electrode) the coloured spot is formed?

(c) Which effect of electric current is involved in this case?

In the process of purification of copper metal, a thin plate of pure copper and a thick rod of impure copper are used as electrodes, and a metal salt solution is used as an electrolyte:

(a) Which electrode is connected to the positive terminal of the battery?

(b) Which electrode is connected to the negative terminal of the battery?

(c) Which metal salt solution is taken as electrolyte?

A student had heard that rainwater is as good as distilled water. So, he collected some rainwater in a clean glass beaker and tested it. To his surprise he found that the compass needle showed deflection. What could be the reason?

Name three liquids which when tested in the manner shown in figure given along side may cause the magnetic needle of compass to deflect.