5 mL of saturated sodium chloride (NaCl) solution is added to a 4" test tube. Its appearance is recorded. Several drops of concentrated hydrochloric acid (HCl) is added to this solution. Your observations are recorded.
- The Iron (III) Thiocyanate Ion Equilibrium
2 mL of 0.1 M iron (III) chloride (FeCl) solution and 2 mL of 0.1 M potassium thiocyanate (KSCN) solution is added to 100 mL of water in a 250 mL beaker. This stock solution is stirred until it is homogeneous. Observations are recorded.
5 mL of the stock solution is added to a 4" test tube (Tube 1). 20 drops of 0.1 M iron
(III) chloride (FeCl3) solution is added to this solution. The observations are recorded. 5 mL of the stock solution is added to a 4" test tube (Tube 2). 20 drops of 0.1 M potassium thiocyanate (KSCN) solution is added to this solution. The observations are recorded. 5 mL of the stock solution is added to a 4" test tube (Tube 3) and then 5 drops of 6 M sodium hydroxide (NaOH) solution is added. Observations are recorded. 2 drops of a 50% sodium hydroxide (NaOH) solution is added to Tube 2. Any changes occur is recorded. Then 5 drops of 12 M hydrochloric acid (HC1) is added and observations are recorded.
- The Acetic Acid Equilibrium
3 mL of a 0.1 M acetic acid (HC2H3O2) solution is added to each of three 4" test tubes. A few drops of methyl orange solution are added to each of the tubes, and the tubes is agitated until the solutions are homogeneous and observations are recorded. A few crystals of sodium acetate (NaC2H3O2) is added to the first test tube (Tube 1). The tube is agitated in order to dissolve the solid. Observations are recorded. A few crystals of sodium chloride (NaCl) is added to the second test tube (Tube 2). The tube is agitated in order to dissolve the solid. Observations are recorded. A few drops of 6 M sodium hydroxide (NaOH) is added to the third test tube (Tube 3). The tube is agitated and observations are recorded.
- The Chromate-bichromate Equilibrium
5 mL of a 0.1 M potassium chromate (K2CrO4) solution is added to a 4" test tube. Its colour is observed and recorded. 6 M nitric acid (HNO3) solution one drop at a time is added to this solution, until a distinct change is noted. Observations are recorded. Then, 6 M sodium hydroxide (NaOH) solution one drop at a time is added to the same test tube, until once again a distinct change has been observed. Again, observations are recorded.
- The Bismuth Chloride-Water Equilibrium
Add 2 mL of distilled water is added into, a 6" test tube. Agitate the tube of water, which consist of a small crystal of bismuth chloride (BiCl3) and record observation. In the next mixture, 12 M of hydrochloric acid (HCl) is added at a time, while agitating the test tube. Observation is then recorded. Later on, added a drop of water at a time while agitating the test tube till there’s a distinct change. Observation is then recorded as well.
- The Cobalt (II) chloride Equilibrium:
5 drops of a 1 M cobalt (II) chloride (CoCl2) solution, is added in a 4" test tube. Observation is then recorded. 12 mL of hydrochloric acid (HC1) is dropped into the mixture at a time while agitating it. Observation is then recorded. Finally, a drop of water at a time while agitating the test tube. Observation is also then recorded.
5.0 Results & Discussion:
Results:
- The Saturated Sodium Chloride Solution Equilibrium
- The Iron (III) Thiocyanate Ion Equilibrium
- The Acetic Acid Equilibrium
- The Chromate-bichromate Equilibrium
- The Bismuth Chloride-Water Equilibrium
- The Cobalt (II) chloride Equilibrium
Discussion:
From Le Chatelier's Principle, if a dynamic equilibrium is disturbed by changing the conditions such as concentration will result in predictable and opposing changes in the system in order to achieve a new equilibrium state. In other words, whenever a system in equilibrium is disturbed, the system will adjust itself in such a way that the effect of the change will be reduced or moderated. By applying Le Chatelier's Principle with a change of concentration, an equilibrium established between four substances A, B, C and D.
According to Le Chatelier’s principle, adding additional reactant to a system will shift the equilibrium to the right, towards the side of the products. By the same logic, reducing the concentration of any product will also shift equilibrium to the right. When increasing the concentration of A, the position of equilibrium will move in such a way as to counteract the change. That means that the position of equilibrium will move so that the concentration of A decreases again by reacting it with B and turning it into C + D. The position of equilibrium moves to the right.
When increase the concentration of A, the position of equilibrium moves to the right.
In contrast, when additional product is added into a system, the equilibrium will shift to the left in order to produce more reactants. Besides, when reactants removed from the system, the equilibrium will be shifted to the left. For example, by decrease the concentration of A, the position of equilibrium will move to left. Thus, the concentration of A increases again and more C and D will react to replace the A that has been removed.
When decrease the concentration of A, the position of equilibrium moves to the left.
When one of the products is removed as soon as it was formed, the position of equilibrium will move to the right to replace it. If the product keeps being removed, the equilibrium position would keep on moving rightwards and turn the chemical reaction into a one-way reaction.
6.0 Conclusion:
In a nutshell, we are able to understand dynamic equilibrium and Le Chatelier's Principle throughout the experiment. We are able to define dynamic equilibrium in which the reaction rate of the forward reaction is equal to the reaction rate of the backward reaction. Besides, we are able to observe the change of an equilibrium when the concentration of a reactant or product is altered. For example, if the concentration of a reactant is increased, the equilibrium will shift in the direction of the reaction that uses the reactants, so that the reactant concentration decreases in order to maintain equilibrium. In contrast, if the concentration of a reactant is decreased the equilibrium will shift in the direction of the reaction that produces the reactants, so that the reactant concentration will increases. Furthermore, we are able to predict the effect of concentration changes on chemical equilibrium. If the concentration of a substance is changed, the equilibrium will shift to minimise the effect of that change. Moreover, we are able to prepare various molar concentration of solution by using suitable formula.
7.0 References:
References
- Van Zeggeren, F.; Storey, S. H. (1970). The Computation of Chemical Equilibria.
Cambridge University Press. Mainly concerned with gas-phase equilibria.
- Leggett, D. J., ed. (1985). Computational Methods for the Determination of Formation Constants. Plenum Press.
- Atkins, Peter; De Paula, Julio (2006). Atkins' Physical Chemistry (8th ed.). W. H. Freeman. pp. 200–202. ISBN 0-7167-8759-8.
- Atkins, Peter W.; Jones, Loretta. Chemical Principles: The Quest for Insight (2nd ed.).
ISBN 0-7167-9903-0.
Appendix
- The Saturated Sodium Chloride Solution Equilibrium
NaCl NaCl + HCl
-
The Iron (III) Thiocyanate Ion Equilibrium
Stock Solution Stock Solution + FeCl3
solution
Stock Solution + KSCN solution
Stock Solution +
NaOH Solution
Stock Solution +
KSCN Solution + 50% NaOH Solution
Stock Solution +
KSCN Solution + 50% NaOH Solution
+ HCl
- The Acetic Acid Equilibrium
Stock Solution Stock Solution + NaC2H3O2
Stock Solution +
NaCl
Stock Solution +
NaOH
- The Chromate-bichromate Equilibrium
K2CrO4 K2CrO4 + HNO3 K2CrO4 + HNO3 + NaOH
- The Bismuth Chloride-Water Equilibrium
Water + BiCl3 Water + BiCl3 Water + BiCl3 +
Water
- The Cobalt (II) chloride Equilibrium
CoCl2 CoCl2 + HCl CoCl2 + HCl + Water
8.0 EXERCISE:
- In your own words, explain Le Chatelier's Principles.
In a broad perspective, Le Chatelier principle is stated that, if the external parameter of a system in equilibrium changes such that the system is no longer in equilibrium, the system behaves in a way to reduce the external effect. However, if the water vapour is equilibrium with liquid water, under an increase amount of apply pressure, more vapour will condense in order to reduce the pressure.
-
What would occur if a few drops of saturated Na2SO4 solution were added to a saturated NaCl solution?
One must know, sodium sulphate (Na2SO4) and sodium chloride (NaCl), are both ionic compounds that are soluble in aqueous solution. Which means that in a solution of sodium sulphate, the salt will unite completely to form sodium cations, Na+, and sulphate anions, SO2−4.
Na2SO4(aq]→2Na+(aq]+SO−4(aq]
In conjunction, sodium chloride will unite completely in aqueous solution to form sodium cations and chloride anions, Cl−
NaCl(aq]→Na+(aq]+Cl−(aq]
However, since both ionic compounds exist as cations and anions in solution, mixing two solutions will not result in a reaction because, all ions will continue to exist as ions in the solution. Simply put, there is no compound that can be formed by mixing these two solutions. All the ions present on the reactants' side will also be present as ions on the products' side.
2Na+(aq] +SO−4(aq]+Na+(aq]+Cl−(aq]→N.R.
In order for a double replacement reaction to take place here, two of the ions need to form an insoluble solid that precipitates out of solution.
- In procedure D3, explain the reason for the change you observed.
When solid potassium chromate, (K2CrO4) is dissolved in water it forms a yellow solution.
2-
This are the colour that came from the negative ions: CrO42-(aq) and Cr2O7
(aq). However, in
solution these ions are actually in equilibrium. The reason for the change is because, when adding (NaOH) solution, the (NaOH) removes H+ ions, because of acid-base neutralization. Adding (NaOH) is equivalent to reducing the [H+ (aq)] in the reaction.
by
petraatosgmailcom (student)
