Le Châtelier's Principle CPR Essay
E_382251
LeChatelier.docx[文件標題]
Le Chatelier’s Priciple Lab Report
Propose:
This experiment is to offer the observation of shifts in equilibrium systems with changes in concentration and temperature, and to use Le Chatelier Principle to explain these shifts.
Procedure:
There will be four systems used in this experiment. For the first two systems, the amounts of reactants and products will be monitored by colored transition-metal complexs, and the direction of equilibrium shifts will be determined based on color changes. For the last two systems, weak-acid and weak-base equilibrium systems and the common ion effects will be used to monitor shifts in pH value, and changes in the concentrations of hydronium or hydroxide ions will explain the shifts in the equilibrium systems.
Experiment:
Part I – The [CoCl4]2- Equilibrium System
[Co(H2O)6]2+(aq) + 4Cl-(aq) [CoCl4]2-(aq) + 6H2O(l)
pink blue
|
Solution |
Observation |
|
CoCl4 solution in six test tubes |
Solutions are in purple color, with the combination of two ions, Co2+ and Cl- |
|
Cold and hot water in two bakers |
Colorless solution |
|
Change Imposed |
Observation |
Explanation |
|
Water added into test tube #2 |
Color of solution turned pink |
H2O added into the system, thus cause the equilibrium shift left. |
|
Concentrated HCl added into test tube #3
|
Color of solution turned blue |
Cl- added into the system, thus cause the equilibrium shift right in order to consume added Cl- |
|
Test tube #4 is placed into hot water |
Color of solution turned blue |
Heat added into the system, thus cause the equilibrium shift right in order to consume added heat |
|
Test tube #5 is placed into cold water |
Color of solution turned pink |
Heat removed from the system, thus cause the equilibrium shift left in order to replace heat removed. This is an endothermic reaction |
|
NaCl(s) added into the tube #6 |
Color of solution turned blue |
NaCl added into the system, some Cl- ion dissolved caused the equilibrium shift right in order to consume Cl- added |
Part II – The [FeSCN]2+ Equilibrium System
Fe3+(aq) + SCN-(aq) [FeSCN]2+(aq)
light yellow red
|
Solution |
Observation |
|
Mixture of solution of Fe(NO3)3 and solution of KSCN |
The color of mixed solution is orange with the combination of Fe3+ and SCN-, and color of orange indicated the equilibrium |
|
Change Imposed |
Observation |
Explanation |
|
Fe(NO3)3 added into baker #2 |
Color of solution turned red |
Fe3+ added into the system, thus caused the equilibrium shift right in order to consume the Fe3+ added |
|
KSCN added into baker #3
|
Color of solution turned red |
SCN- added into the system, thus caused the equilibrium shift right in order to consume the SCN- added |
|
Na2SO3 added into baker #4 |
Color of solution turned light yellow |
SO32- added into the system, thus caused Fe3+ changed into Fe2+, equilibrium shift left to replace Fe3+ removed |
|
F- added into baker #5 |
Color of solution turned colorless |
F- added into the system, thus caused Fe3+ changed its charge, equilibrium shift left to replace Fe3+ removed |
|
Ag+ added into baker #6 |
Color of solution turned milky white |
Ag+ added into the system, thus caused SCN- react with it to form solid AgSCN, equilibrium shift left to replace SCN- removed |
Part III – The Ammonia-Ammonium Ion Equilibrium System
NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)
|
Solution |
Observation |
|
NH3 solution in test tube are colorless |
Solution of test tubes are colorless before adding anything into them |
|
Solutions were added with phenolphthalein |
Color of solution turned dark pruple |
|
Change Imposed |
Observation |
Explanation |
|
3M of HCl added into test tube #1 |
Solution in test tube #1 turned colorless |
HCl added caused the solution to become more acidic, pH decreased, the equilibrium shift right since H+ reacted with OH- to create H2O |
|
Small amount of NH4Cl added into test tube #2
|
Solution in test tube #2 turned light pink |
NH4+ added caused the solution to become more acidic, pH decreased, the equilibrium shift left in order to consume NH4+ added |
|
0.1M of NaOH added into test tube #3, then 0.1M of HCl added |
Solution in test tube #3 stayed dark purple, and the color turned colorless after HCl added |
OH- added caused the solution to become more basic, pH increased, the equilibrium shift left to consume OH- added. |
Part IV – The Acetic Acid – Acetate Ion Equilibrium System
HC2H3O2(aq) + H2O(l) H3O+(aq) + C2H3O2-(aq)
|
Solution |
Observation |
|
Acetic acid solution is colorless in the baker |
Solution is colorless at first before methyl red was added, after adding methyl red the solution turned pink |
|
Change Imposed |
Observation |
Explanation |
|
1M of NaOH added into the right-most baker |
Color of solution turned colorless after NaOH solution added |
OH- added to cause the solution to become more basic, pH increased, the equilibrium shift left to consume H3O+ to created water with OH- |
|
C2H3NaO2 added into the left-most baker
|
Color of solution turned colorless after C2H3NaO2 dissolved into the solution |
C2H3O2- added to cause the solution to become more basic, pH increased, the equilibrium shift left in order to consume C2H3O2- |
