Theory:

When a single element displaces another element in a compound, this is known as a single displacement or exchange reaction.
 
A + BCAC + B
  
\(Zn\) + \(CuBr_2\) → \(ZnBr_2\) + \(Cu\)    (cation single replacement)
\(Cl_2\) + \(2KI\) → \(2KCl\) + \(I_2\)     (anion single replacement)
Example:
Experiment \(2\)a: To study the chemical reaction of zinc with sulphuric acid.
  
Materials required:
  
-Zinc metal granules
-Dilute sulphuric acid
-Red and blue litmus papers
-Test tube and
-Candle
 
Experimental procedure:
 
Step 1: Take few zinc granules in a test tube.
Step 2: Add about \(10\) mL of dilute sulphuric acid to zinc granule. Effervescence comes out from the reaction mixture, as shown in the below figure.
 
 pic 15.png
The reaction of zinc granules with dilute sulphuric acid
 
Step 3: Perform the tests as given in the observation table and record your observations.
 
Observation:
  
No.
Test
Activity
Observations
1
ColourLook at the colour of the gas liberatedColourless gas is evolved (effervescence).
2
SmellFan the gas gently towards your nose with your handOdourless gas is observed.
3
Litmus testBring moist blue and red litmus papers near to the mouth of the test tubeDoes not change the colour of the litmus papers.
4
Combustion testBring a lighted candle near to the mouth of the test tubeThe liberated gas produces a pop sound and turns off the candle.
  
Result:
Zinc metal reacts with dilute sulphuric acid to produce zinc sulphate and hydrogen gas.

\(Zn\)(s) + \(H_2SO_4\)(aq) → \(ZnSO_4\)(aq) + \(H_2\)(g)

Zinc sulphate formation is an example of a single displacement reaction of a non-metal by a metal.
 
The observation from the above table clearly shows that the produced gas is hydrogen. It is the only gas with these properties; colourless, odourless, does not change the litmus paper (because it is neutral) and turns off the candle.
  
Final result:
  
From the above observation, the nature of the produced gas is neutral because it does not change the colour of the litmus paper.
Hydrogen is flammable. When hydrogen burns (or externally ignites) in the air to produce water and heat, this process is called combustion.
Conclusion:
 
We already know what a single displacement reaction is. The above experiment clearly shows the single displacement reaction. Here zinc has displaced another element in a compound, sulphate, from dilute sulphuric acid.