This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Lime Soda Process”.
1. What is the molecular formula of lime?
Explanation: The molecular formula of lime is Ca(OH) 2. It is a white caustic alkaline substance consisting of calcium oxide, which is obtained by heating limestone and which combines with water with the production of much heat.
2. What is the molecular formula of soda?
c) Mg(OH) 2
d) Ca(OH) 2
Explanation: The molecular formula of soda is Na2CO3. It is also called washing soda or soda ash.
3. Which of the following is not a precipitate in lime-soda process?
b) Fe(OH) 3
c) Al(OH) 3
Explanation: Al2(SO4)3 is not a precipitate in lime-soda process. All the other options are the precipitate in lime-soda process.
4. Which of the following is not used as a coagulant in lime-soda process?
b) Calcium bicarbonate
c) Aluminium sulphate
d) Sodium aluminate
Explanation: Calcium bicarbonate is not used as a coagulant in lime-soda process. Alum, aluminium sulphate and sodium aluminate are used as coagulants in lime-soda process.
5. What is the function of coagulant?
a) It helps in the formation of fine precipitate
b) It helps in the formation of coarse precipitate
c) It helps in increasing the solubility
d) It helps in increasing the boiling point
Explanation: Coagulants helps in formation of coarse precipitate. C?oagulation is a process of addition of coagulant to destabilize a stabilized charged particle.
6. For the softening of one mole of magnesium bicarbonate, the number of mole of lime required is
Explanation: For the softening of one mole of magnesium bicarbonate, the number of mole of lime required is two. The ratio of bicarbonate to lime in lime-soda process is 1:2.
7. The residual hardness in lime-soda process is
a) 0-2 ppm
b) 5-15 ppm
c) 15-50 ppm
d) 50-70 ppm
Explanation: The residual hardness in lime-soda process is 15-50 ppm. Lime soda softening cannot produce a water at completely free of hardness because of the low solubility of CaCO3 and Mg(OH)2.
8. In lime soda process, capital cost is ___________ whereas operational expenses are __________
a) High, low
b) High, high
c) Low, low
d) Low, high
Explanation: In lime soda process, capital cost is low whereas operational expenses are high. It is because the chemicals and reagents used are costly.
9. In lime-soda process, no exchange of ions occurs.
Explanation: In lime-soda process, no exchange of ions occurs. Recarbonation is used to stabilize the water. The excess lime and magnesium hydroxide are stabilized by adding carbon dioxide, which also reduces pH from 10.8 to 9.5.
10. Which of the following is the second step for calculating the amount of lime and soda?
a) Identification of lime and soda for different salts
b) Calculation of CaCO3 equivalents
c) Calculation of lime requirements
d) Calculation of soda requirements
Explanation: Calculation of CaCO3 equivalents is the second step for calculating the amount of lime and soda. First step is to identify the lime and soda for different salts. and the last two steps are calculation of lime and soda requirements.
Sanfoundry Global Education & Learning Series – Engineering Chemistry.
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