Chemistry - Study Mode

[#486] The amount of chlorine available in water after disinfection is called as
Correct Answer

(B) Residual chlorine

Explanation

Solution: The word “residual” means “remainder” or “that which is left”, and as the name suggests the chlorine residual is measure of the amount of chlorine remaining in the water after disinfection. The chlorine residual is usually tested in finished water which is ready to be released into the distribution system, although operators must also ensure that there is adequate residual at the extreme ends of the distribution system. Tests for chlorine residual are probably the most frequently performed tests at water treatment plants. There are three types of chlorine residual which must be considered in water treatment. Free chlorine residual - residual consisting of dissolved chlorine gas, Hypochlorous acid, and hypochlorite ions, Combined chlorine residual - residual consisting of other forms of chlorine such as chloramines which are capable of killing bacteria and oxidizing organic matter, Total chlorine residual - the sum of the free chlorine residual and the combined chlorine residual.

[#487] Maximum permissible concentration of total hardness in drinking water is
Correct Answer

(C) 200

Explanation

Solution: Maximum permissible concentration of total hardness in drinking water is 200.

[#488] Which one of the following is extensively used for sterilizing water ?
Correct Answer

(A) Bleaching powder

Explanation

Solution: Bleaching powder is extensively used in sterilizing water. Calcium hypochlorite is a chemical compound with formula Ca(OCl) 2 . It is widely used for water treatment and as a bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach). Calcium hypochlorite is a yellow white solid which has a strong smell of chlorine. It is not highly soluble in water, and is more preferably used in soft to medium-hard water. It has two forms: a dry form and a hydrated form. The hydrated form is safer to handle.

[#489] Assertion (A) : Synthetic detergents can lather when in hard water. Reason (R) : Synthetic detergents form soluble calcium and magnesium salts with hard water.
Correct Answer

(A) Both A and R is true and R is the correct explanation of A

Explanation

Solution: Both A and R is true and R is the correct explanation of A.

[#490] The buffer action of blood is due to the presence of
Correct Answer

(D) [HCO 3 ] – and H 2 CO 3

Explanation

Solution: Human blood contains a buffer of carbonic acid (H 2 CO 3 ) and bicarbonate anion (HCO 3 - ) in order to maintain blood pH between 7.35 and 7.45, as a value higher than 7.8 or lower than 6.8 can lead to death. In this buffer, hydronium and bicarbonate anion are in equilibrium with carbonic acid. Furthermore, the carbonic acid in the first equilibrium can decompose into CO 2 gas and water, resulting in a second equilibrium system between carbonic acid and water. Because CO 2 is an important component of the blood buffer, its regulation in the body, as well as that of O 2 , is extremely important. The effect of this can be important when the human body is subjected to strenuous conditions. Source : chem.libretexts.org