8. which of the following is a method of purifying water?

a. adding iodine
b. freezing
c. aeration
d. fixation

is a method of purifying water.

Further Explanation:

A. Adding iodine

Iodine is a mineral which is found in food and is essential for body. It is important in both radioactive and non-radioactive forms. Iodine, in its elemental state is used as a disinfectant. Its deficiency can lead to mental disabilities in children and less formation of thyroid hormone.

B. Freezing

When a substance gets converted from its liquid to a solid state, it is called freezing. This is done by lowering the temperature of the substance below its freezing point. For example, ice is formed from water by the process of freezing.

C. Aeration

In this technique, air is allowed to dissolve in the liquid. This is done by passing air through aeration turbines. Due to this process, water and air are brought closer to each other and as a result, dissolved gases are removed from the water. It is the initial step at the water treatment plant. It is also useful to remove dissolved metals via oxidation, followed by filtration.

D. Fixation

When a specimen is allowed to fix with chemicals so as to avoid autolysis during the preparation of the specimen, the process is called fixation. It has to be carried out just after the removal of tissues to avoid autolysis.

Therefore aeration is used to purify water.

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Answer details:

Grade: Senior School

Chapter: Methods of purification

Subject: Chemistry

Keywords: aeration, fixation, iodine, freezing, purify, water, solid, liquid, specimen, autolysis, air, aeration tubes.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.