This set of Applied Chemistry Questions and Answers for Campus interviews focuses on “Estimation of Hardness – 2”.
1. Estimation of hardness can be determined by ________ types.
Explanation: Estimation of hardness can be determined by two types. They are Soap titration method and EDTA method.
2. Total hardness of water can be determined by titrating the fixed volume of water against the standard ___________ solution.
b) Alkaline soap
c) Acidic soap
d) Alcoholic soap
Explanation: Total hardness of water can be determined by titrating the fixed volume of water against the standard alcoholic soap solution.
3. The end point of the titration in the soap titration method is ___________
a) Formation of lather
b) Formation of salts
c) Formation of carbonates
d) Formation of bicarbonates
Explanation: The end point of the titration in the soap titration method is at the formation of lather that stands for about two minutes.
4. The sodium soap will precipitate all the hardness causing ions into their respective __________
Explanation: The sodium soap will precipitate all the hardness causing ions into their respective stereates in the beginning of the soap titration method.
5. The water which form lather directly with the soap is called __________
a) Hard water
b) Soft water
c) Partially hard water
d) Very hard water
Explanation: The water which forms lather directly with the soap is called soft water. The water which forms precipitates when reacted with soap is called as the hard water.
6. EDTA method is also called as _________
a) Complexometric titration
b) Complex titration
c) Complement titration
d) Complexion titration
Explanation: EDTA method is also called as the complexometric titration. In EDTA method is ethylene diamine tetra acetate is the compound used to remove the hardness.
7. The indicator used in the EDTA method is ___________
c) Ethylene diamine
d) Erichrome black T
Explanation: The indicator used in the EDTA method is erichrome black T. The hardness causing ions like Ca++ and Mg++ forms the unstable complexes with reacting the erichrome black T.
8. EDTA has the ability to form _________ with metal ions.
a) Stable complexes
b) Unstable complexes
Explanation: EDTA has more affinity to form stable complexes by reacting with metal ions. The EDTA forms the stable EDTA complexes.
9. The colour of dye metal complex and dye are ___________
c) Same in only some cases
d) Cannot be known
Explanation: The colour of dye metal complex and dye are different. EDTA extracts the metal ions from the metal ion dye to form stable complex.
10. The change in colour is sharper at the PH of ________
Explanation: The change in the colour of the ions is sharper at the PH of the 10 than that of the other ranges of the PH.
11. At PH=10, the metal dye complex has the colour ________
a) Wine red
Explanation: At the PH=10, the metal dye complex ion has the colour is wine red but the dye itself has the blue colour at the PH of 10.
12. To prepare EDTA solution _________ grams of EDTA is dissolved in the one litre of water.
Explanation: To prepare EDTA solution, four grams of the EDTA is dissolved in the one litre of the water. This is the standard EDTA solution used to determine the hardness of water.
13. _________ drops of indicator is used in the EDTA method.
a) 1 to 2 drops
b) 2 to 3 drops
c) 2 to 4 drops
d) 5 to 8 drops
Explanation: 1 to 2 drops of the indicator is used in the EDTA method. 0.5gms of the dye is dissolved into the 100ml of alcohol and the indicator of two to three drops is added.
14. The buffer used in the EDTA solution must have the PH of ___________
Explanation: The buffer used in the EDTA solution must have the PH of 10. Freshly prepared solutions are more affective to have the accurate results.
15. The standard hard water is prepared such that each ml must contain ________ mg of CaCO3.
Explanation: The 1g of pure CaCO3 is dissolved in the minimum amount of concentrated HCL diluted to 1ltr of distilled water such that it contains 1mg of CaCO3.
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