The approximate % of calcium oxide in fat lime is
- A90 - 95%Correct
- B80 - 85%
- C75 - 80%
- D70 - 75%
Solution
Concept
Fat lime (high calcium lime) is nearly pure CaO, about 95% CaO with less than 5% impurities.
Step-by-step solution
1. Fat lime is also called high calcium lime or pure lime. 2. It has very few impurities, usually less than 5%. 3. So its CaO content is about 95%. 4. Among the options, 90-95% is the closest. Answer is (A).
Explanation
Fat lime is a very pure form of lime. It contains about 95% calcium oxide and very little clay. It slakes fast and its volume increases 2 to 2.5 times.
Why the other options are wrong
B, C and D: These CaO values are too low. Lime with more impurities is lean (poor) or hydraulic lime, not fat lime.
Shortcut
Fat lime = pure lime = about 95% CaO.
Common mistake
Mixing up fat lime with hydraulic lime, which has more clay.
Correct answer: A) 90 - 95%