SHANMUGANATHAN ENGINEERING COLLEGE An IS

Reg. No.

SHANMUGANATHAN ENGINEERING COLLEGE
(An ISO 9001:2008 Certified Institution)
ARASAMPATTI – 622 507
WEEKLY TEST-I (ANSWER KEY)
BRANCH
YEAR/SEM
DATE
TIME

: Common to all
: /I
: 18/09/2017
: 09.15am – 10.05 am

SUB CODE
: CY8151
SUB TITLE : Engineering Chemistry
Q.P SETTER : S.Meenakshi, AP
MAX. MARKS: 25

Answer ALL Questions
PART – A (6 x 2 = 12)

1. What are the salt responsible for carbonate & non-carbonate hardness of water?
Carbonate hardness: Ca(HCO)2 and Mg(HCO)2
Non-carbonate hardness : CaSO4 , MgSO4 , CaCl2 , MgCl2
2. Distinguish between Hard water and Soft water.
Hard water
Hard water does not produce lather with soap

Soft water
Soft water produces very good lather with soap

solution
It give wine red colour with EBT indicator

solution
It does not give colour with EBT indicator

3. How hardness of water is expressed?

The concentration of hardness producing salts are usually expressed interms of an equivalent
amount of CaCO3
Amount equivalent to CaCO3 = X x molecular weight of CaCO3
molecular weight of hardness producing substance
4. Write the disadvantages of using hard water in boilers.
a. Scale and sludgeb. Priming and Foaming
c. Caustic embrittlement
d. Boiler corrosion

5. Difference between internal conditioning and external conditioning methods.
Internal Conditioning
External Conditioning
Its carried out with in the boiler
Its carried out before feeding the water into the boiler
It is used for low pressure boilers
It is used for high pressure boilers
It requires blow down operation
blow down operation is not required
6. Calculate the hardness of a water sample containing 2.4 mg of CaCl2 in 500 ml of water.
The amount of CaCl2 =2.4 mgs/500 ml

(or)
The amount of CaCl2 =4.8 mgs/1 lit
Molecular weight of CaCl2 = 111
Amount equivalent to CaCO3 = X x molecular weight of CaCO3
molecular weight of hardness producing substance
Amount equivalent to CaCO3 = 4.8 x 100
111
= 4.324 mgs/lit
PART -B (1 x 13 = 13)
7. (a) Explain the EDTA method of estimation of hardness of water

(13)

Formula (2)
Principle (2)
Procedure (5)
Calculation (4)

(OR)

(b) (i) How is internal treatment of boiler water carried out using Phosphate and Sodium
aluminate conditioning.
Phosphate conditioning

(08)
(4)

Sodium aluminate conditioning (4)
(ii) What are Scale and Sludges . Describe the disadvantages of scale formation.

(05)

Scale (3)
Sludge (2)

STAFF IN-CHARGE

HoD-CHEMISTRY