344.  The pH value of water during chlOrination is generally maintained slightly less than
A.5
B.7
C.9
D.10

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345.  Chlorination of water containing ammonia of pH value less than 7 predominates
A. mono chloramine (NH2C1)
B. di-chlorarnine (NHC12)
C. nitrogen trichloramine (NC13)
D. All the above.

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346.  Pick up the correct statement from the following :
A. The combined chlorine is 25 times less effective in disinfectant than free chlorine
B. The amount of chlorine used in reducing organic as well as inorganic impurities, is called the chlorine demand of water.
C. The hypochlorites, the free chlorine residual, acts as disinfectant to kill pathogens for disinfection of water
D. 0.2 mg/lis quite satisfactory, 10 minutes after chlorination of water.

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347.  The chlorine demand of water is decided by the following factor :
A. Chlorine required for reducing organic impurity
B. Chlorine required for reducing inorganic impurity
C. A minimum of 0.2 mg,/1 /residual, is required after chlorination.
D. Total dose (in mgl) minus the free residual

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348.  If the polluted water contains the organisms which cause amoebic dysentery, we recommend
A. prechlorination
B. post chlorination
C. break-point chlorination
D. super chlorination

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349.  Which one of the following tests is carried out to test the amount of residual chlorine left in chlorinated water after the required contact period
A. Orthotolidine test
B. D.P.D. test
C. Chlorotex test
D. All the above.

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350. In which of the following tests for chlorine residuals is used sodium arsenite :
A. Orthotolidine test
B. D. .D. test
C. Chlorotex test
D. St ch-iodide test

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