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Chapter: 9th Science : Chemistry : Applied Chemistry

Answer the following questions

Science : Chemistry : Applied Chemistry : Book Back Important Questions, Answers, Solutions : Answer briefly, Answer in detail, Exercise Numerical Problems, Intext Activities




IV. Answer briefly:


1. What is Radio Carbon Dating?

Answer: Radio carbon dating is a method by which the age of fossil wood or animal is determined using C-l4 isotope.


2. What are called Anaesthetics? How are they classified?

Answer: The drugs which cause loss of sensation is called Anaesthetics.

Classification: Anaesthetics are classified according to the area of application as,

1. General Anaesthetics,

2. Local Anaesthetics.


3. What is the need for chemical fertilizers in crop fields?

Answer: The need for chemical fertilizers in crop fields is to supply essential micro and macro nutrients required for crop growth.

4. What is Forensic chemistry related to?

Answer: Forensic chemistry is related to application of scientific principles, techniques and methods to the investigation of crime.


V. Answer in detail:


1. Explain the types of dyes based on their method of application.


1. Acid Dyes:

1. These are acidic in nature.

2. They are used for dyeing animal fibres and synthetic fibres.

3. These can be used for protein fibre such as wool and silk.

Example: Picric acid, Naphthol yellow-s.

2. Basic Dyes:

1. These are basic dyes containing basic group .( −NH2, NHR, −NR2)

2. They are used for dyeing animal fibres and plant fibres.

(Example: Crystal violet, Methlyene Blue).

3. Mordant dyes (or) Indirect Dyes:

1. These dyes have a poor affinity for cotton fabrics and hence do not dye directly.

2. They require pretreatment of the fibre with a mordant.

3. Mordant is a substance which can be fixed to the fibre and then can be combined with the dye to form an insoluble complex called lake. Salts of aluminium, chromium and iron are used as mordants.

Example: Alizarin.

4. Direct Dyes:

1. They have high affinity for cotton, rayon and other cellulose fibre.

2. So they are applied directly as they fix firmly on the fabric.

Example: Congo red.

5. Vat Dyes:

1. It can be used only on cotton and, not on silk and wool.

2. This dyeing is a continuous process and is carried out in a large vessel called vat.

3. So it is called as Vat dye.

Example: Indigo 


2. Name various food additives and explain their functions.



VI. Higher Order Thinking Skills:


1. Batteries that are used in mobile phone can be recharged. Likewise, can you recharge the batteries used in watches? Justify your answer.

Answer: The type of batteries used in watches is Primary cell. (Mercury-Oxide battery)

The type of batteries are used in mobile phone is Secondary cell. (Lithium -ion polymer battery)

The differences between primary and secondary cell are as follow:

Primary Cell

1. The chemical reaction of primary cell is irreversible.

2. Hence it can not be recharged.

Secondary cell

1. The chemical reaction is reversible.

2. Hence it can be recharged.


2. Sudha met with a fire accident. What kind of drug(s), she must take?


1. Antibiotic ointments must be used to treat the burns.

2. Analgesic tablets can be taken to relieve from pain.

3. Antiseptic creams can be given to prevent infection.


3. The soil pH of a crop land is 5. What kind of fertilizers should be used in that land?

Answer: 1. pH of 5 indicates the soil is Acidic.

2. So alkaline fertilizers should be used.

(e.g.,) Potash fertilizers, Nitrogen fertilizers. 


Intext Activities



With the help of your teacher, construct the galvanic cell using lemon and potato. Identify their anode, cathode and electrolyte.

Aim: To construct a galvanic cell using lemon (or) potato.

Materials required:

1. A large fresh juicy lemon,

2. Zinc coated nail,

3. Small copper coin,

4. LED light,

5. Connecting wires.


1. Insert the copper coin into the lemon.

2. Push a zinc coated nail into the other side of the lemon.

3. The copper coin and zinc coated nail are connected to low voltage LED bulb.

4. Now observe the results, (happenings).


1. Copper coin acts as cathode, zinc coated nail acts as Anode. Lemon juice act as electrolyte.

2. We observe glow of LED light, which confirms the electricity to flow through the lemon.


 Galvanic cell using lemon is constructed.


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