To perform and observe the following reactions and classify them into:
i. Combination reaction
ii. Decomposition reaction
iii. Displacement reaction
iv. Double displacement reaction

A. Action of water on quicklime
B. Action of heat on ferrous sulphate crystals
C. Iron nails kept in copper sulphate solution
D. Reaction between sodium sulphate and barium chloride solutions.

Experiment A

Aim: To perform and observe the action of water on quicklime and also to identify the type of reaction involved.

Apparatus and Chemicals:

  • 250 mL beaker
  • China dish
  • Asbestos sheet
  • Dropper
  • Quick lime
  • Water

Principle

Quicklime is calcium oxide, CaO. It reacts with water to give calcium hydroxide, Ca(OH)2. The reaction is exothermic in nature.
CaO + H2O → Ca(OH)2

This is an example of combination reaction, in which two reactants i.e., calcium oxide and water, react to give one product i.e., calcium hydroxide.

Procedure

  • Take some (5-10 g) of quicklime in a clean and dry china dish. You need not powered it, even it is lumply.
  • Place the china dish on an asbestos sheet.
  • Take some water in a beaker. With the help of a dropper sprinkle some droops (4-5 drops) of water on a quick lime in the china dish.
  • Carefully record your observations in the note book.

Observations

S.No. Experiment Observation
1. Note the evolution or absorption of heat — if any, during the reaction by touching the china dish before
and after the experiment.		 The china dish becomes hot after the reaction. indicating that the reaction is exothermic in nature.
2. Note the evolution of any gas or vapour during the reaction. A part of the water added is converted into steam by the heat of the reaction.
3. Note the sound produced — if any, during the reaction A hissing sound is produced during the reaction.
4. Note the physical changes produced — if any, in the reactants
during the reaction		 The lumply quick-lime crumbles to give a fine powder. A part of the water added turns into steam due to the heat produced during the reaction.

Inference : The reaction between quicklime (calcium oxide) and water is an exothermic reaction. In this reaction calcium oxide and water reacts to give calcium hydroxide. The reaction is accompanied by a hissing sound. This is an example of combination reaction.

Precautions

  • China dish should be clean and dry before before the experiment.
  • Do not add too much water.
  • Sprinkle water carefully over the quick lime and protect yourself from the hot steam formed during the reaction.
  • Touch the hot china dish carefully after the experiment.