1. Carbonate hardness can be removed by adding lime to water.
a) True
b) False
Explanation: Carbonate hardness is due to the presence of carbonates and bicarbonates of calcium and magnesium in water and can be removed by boiling or by adding lime to it.
2. Which of the following statement is wrong regarding permanent hardness?
a) It is also called carbonate hardness
b) It is due to the presence of sulfates, chlorides and nitrates of calcium and magnesium
c) It cannot be removed by boiling
d) It requires special methods of water softening to get removed
Explanation: Permanent hardness is called non-carbonate hardness whereas temporary hardness is called carbonate hardness.
3. One degree of hardness is equivalent to ___ ppm.
a) 2
b) 1
c) 10
d) 100
Explanation: Water is said to have one degree of hardness when its soap destroying power is equivalent to the effect of 14.25mg of calcium carbonate in one litre of water.
4. In which method of determining total hardness of water is based on the premise that hardness producing substance react with soap and form insoluble compounds before lather is produced?
a) Clark’s method
b) Hehner’s method
c) Versenate method
d) EDTA method
Explanation: In Clark’s method, total hardness is found by determining the standard soap solution required to obtain permanent lather with the water sample of known volume.
5. What is the indicator used in EDTA method?
a) Potassium chromate
b) Potassium dichromate
c) Potassium chloride
d) Erio chrome, black T
Explanation: Hardness is determined by using Ethylene diamine tetra-acetic acid using Erio chrome, black T as indicator at a pH between 8.5 and 11
6. The permissible limit of pH preferred for potable water is ___ ppm.
a) 6.5-9
b) 7-8.5
c) 10-14
d) 0-7
Explanation: The permissible limit of pH for potable water should not exceed 9 and should not be less than 6.5 and the preferred limit is 7-8.5
7. What is the concentration of H+ ions in moles/L in water if the pOH value is 6?
a) 10-6
b) 10-7
c) 10-8
d) 10-9
Explanation: pH + pOH = 14
pOH = 6, so pH = 14-6 = 8
H+ = 10-pH = 10-8moles/L.
8. Which type of bacteria has a rod shaped structure?
a) Bacilli
b) Cocci
c) Spirilla
d) Vibrio
Explanation: Bacilli (Singular-Bacillus) has a rod shaped structure. Cocci has a spherically shaped structure, Spirilla has a spiral shaped structure and Vibrio has a comma shaped structure.
9. ________ represents the bacterial density that is most likely to be present in water.
a) BOD
b) COD
c) MPN
d) Coliform index
Explanation: Most Probable Number is a number that indicates the bacterial density present in water.BOD and COD are the terms related to the oxygen required by microorganism to oxidize organic and inorganic matter
10. Which of the following is a better test to identify Coliforms?
a) Coliform index
b) Multiple tube fermentation
c) MPN test
d) Membrane filter technique
Explanation: Membrane filter technique is a better and simpler technique to identify Coliforms. Various results are obtained in a shorter time than the multiple tube fermentation technique. MPN test and coliform index are not used now