HS 1st year : Chemistry chapter 6 Equilibrium experiments

 

Experiment Title:

Study of Chemical Equilibrium – Effect of Concentration on the Position of Equilibrium

Objective:

To observe the effect of changing concentration on the position of equilibrium in a reversible reaction.

Materials Required:

• Iron(III) chloride solution (FeCl₃)

• Potassium thiocyanate solution (KSCN)

• Distilled water

• Test tubes

• Dropper

• Beaker

• Glass rod

Chemical Reaction:

$\text{Fe}^{3+}(aq) + \text{SCN}^-(aq) \rightleftharpoons \text{FeSCN}^{2+}(aq)$
This reaction shows a reddish-brown complex formation, which is reversible.

Procedure:

1. Preparation of Equilibrium Mixture:

   • Take about 5 mL of 0.002 M FeCl₃ solution in a test tube.

   • Add 5 mL of 0.002 M KSCN solution.

   • Mix well and observe the reddish-brown colour of FeSCN²⁺ complex indicating equilibrium.

2. Effect of Adding Reactant (KSCN):

   • Take a small portion of the equilibrium mixture in another test tube.

   • Add a few drops of KSCN solution.

   • Observe the intensification of the reddish-brown colour (due to shift in equilibrium to the right).

3. Effect of Adding Reactant (FeCl₃):

   • Take another portion of the original equilibrium mixture.

   • Add a few drops of FeCl₃ solution.

   • Observe the increase in colour intensity again (shift to the right).

4. Effect of Dilution:

   • Take a third portion of the equilibrium mixture.

   • Add distilled water.

   • Observe the fading of the colour indicating a shift in equilibrium (can be interpreted depending on ion concentration changes).

Observation:

• Addition of either Fe³⁺ or SCN⁻ ions deepens the colour of the complex.

• This confirms that equilibrium shifts to the right (product side) when reactant concentration increases (as per Le Chatelier’s Principle).

Conclusion:

The position of chemical equilibrium is influenced by the concentration of reactants. Increasing the concentration of reactants shifts the equilibrium towards the formation of more product.