Chemistry Worksheet

How is the effect of the concentration to the chemical equilibrium?

A. Objective:

            To see the effect of the concentration change to the chemical equilibrium.

B.  Tools and Materials

            1. Reaction tube                                                              

            2. Pasteur pipette

3. Reaction tube rack                                                         

4. Chemical glass

5. Swirling stick                                                                

6. Aquades

            7. FeCl₃ solution 1M                                                    

            8. KSCN solution 1M

            9. Crystal Na₂HPO₄

 

C.  Steps

1. Pour 50 ml aquades to the chemical glass

2. By using Pasteur pipette, add 4 drops of FeCl₃ solution 1M and 4 drops of KSCN solution 1M into the chemical glass with aquades! Stir it until the color is homogeny.
3. Prepare 5 reaction tubes! Pour each of reaction tube with the same amount of solution from chemical glass. Give it with number I, II, III, IV, and V!
4. Reaction tube number I is used to compare the solution colors.
5. Add 1 drop of FeCl₃ solution 1M to the reaction tube number II!
6. Add 1 drop of KSCN solution 1M to the reaction tube number III!
7. Add crystal Na₂HPO₄ to the reaction tube number IV!
8. Add aquades to the reaction tube number V, save it with reaction tube number I for the next experiment.
9. Compare the solution colors at reaction tube number II, III, and IV to the solution colors at reaction tube number I! Write down your observation!

D. Observation Result

      The chemical equation: Fecl_3(aq) + 3 KSCN_(aq)  FeSCN²⁺_(aq) + 3 KCl_(aq)

No. of the Reaction tube	Treatment	The colors of observation result
I	-	Orange
II	+ 1 drop of FeCl3 1M	Sorrel
III	+ 1 drop of KSCN 1 M	Condensed red
IV	+ Na2HPO4 crystal	Transparent

E.  Question

1. What is the solution color at reaction tube number I?
2. How is the solution color at tube II compared with the solution color of tube I?
3. How is the solution color at tube III compared with the solution color of tube I?
4. How is the solution color at tube IV compared with the solution color at tube I?
5. What is the purpose by adding FeCl₃ at reaction tube number II? Explain!
6. What is the purpose by adding KSCN at reaction tube number III? Explain!
7. What is the purpose by adding crystal Na₂HPO₄ at reaction tube number IV? Explain!
8. What is the conclusion of the observation?
9. How is the equilibrium chemical reaction at this observation?

Answers

1. The solution color at the reaction tube number 1 is orange.
2. The solution color at the reaction tube number 2 is sorrel or become darker.
3. The solution color at the reaction tube number 3 is condensed red or become darker than the solution color at the reaction tube number 2.
4. The solution color at the reaction tube number 4 is transparent or become clear.
5. To see the shift of the chemical equilibrium if one of the concentration of the reactant is bigger.  It shows by the darker color caused the chemical equilibrium shift to the product.
6. To see the shift of the chemical equilibrium if one of the concentration of the reactant is bigger.  It shows by the darker color caused the chemical equilibrium shift to the product.
7. To see the shift of the chemical equilibrium if another substance is added.  It shows by transparent color caused by Na₂HPO₄ bonds the ion Fe³⁺.
8. The concentration change can affect the shift of the chemical equilibrium.  If the concentration of the substances is bigger, the chemical equilibrium will shift away from the substances, and the color of the products will become darker.  In this experiment, the solution color becomes darker when the concentration of the reactant is bigger.  Oppositely, if the concentration of the substances is lower, the chemical equilibrium will shift away to the substances, and the color of the products will become clearer.  In this experiment, the solution color becomes transparent caused by the reduction of the product.
9. The chemical equilibrium shifts by following the Le Chatelier principle.