To perform Action of water on quick lime and classify it - Lab Work

To perform Action of water on quick lime and classify it on Combination reaction, Decomposition reaction, Displacement reaction and Double displacement reaction

Aim
To perform Action of water on quick lime and classify it on:
i. Combination reaction
ii. Decomposition reaction
iii. Displacement reaction
iv. Double displacement reaction

Theory
(a) When water is added slowly to a beaker containing a small amount of CaO the beaker becomes hot.
Reaction:      CaO (s)        +         H2O (l)   →   Ca(OH)2 (aq) + heat
      Calcium oxide(Quicklime)     Water     Calcium hydroxide(Slaked lime)
(b) In this reaction two compounds CaO and H2O combine to give Ca(OH)2, a single product which is an example of combination reaction. Hence it may be stated that when two or more substance(s) combine to form a single product, the reaction is called combination reaction.
(c) It has been observed that a large amount of heat is evolved in course of reaction, such type of reactions are termed as exothermic reaction.

Chemicals Required
Calcium oxide, Water

Apparatus Required
Beaker

Procedure
Step 1: A small quantity of calcium oxide (quick lime) is taken in a beaker.
Step 2: Water is slowly added to the quick lime taken in the beaker. Enough water is poured so that the quick lime remains submerged in the water.
Step 3: Beaker is touched with fingers to note the temperature.
Step 4: The beaker is left undisturbed for some time.

Observation
1. When water is added to quick lime, a suspension of slaked lime is formed.
2. The beaker was hot when it was touched with fingers.
3. A clear solution appears when the suspension of slaked lime settles down to the bottom of the beaker.

Inference
1. the reaction is highly exothermic because quick lime reacts vigorously with water to form slaked lime releasing large amount of heat .
2. Slaked lime is only slightly soluble in water, so it forms a suspension of slaked lime in water.
3. The clear solution obtained after the suspension settles is called lime water.
4. Calcium oxide and water react to form only a single product, calcium hydroxide. So the reaction is a combination reaction.

Precautions
1. Never put quick lime in water. It may cause the lime water to splash out of the container and damage eyes or skin.
2. Always take quick lime in small quantity in a beaker and then slowly pour water on it.
3. Do not add excessive water as it may cause an explosion due to vigorous reaction.
4. Do not touch or dip your fingers in lime water. Calcium hydroxide may burn the skin.

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