Le Châtelier Principle Lab Report
Applications of Le Châtelier's Principle
(September 11 - 15, 2014)
**The purpose of this experiment was to visually observe the effects of how changing certain aspects of the reaction affected the observed equilibrium.
PROCEDURE:
Introductory activity
Part A: Effect of Concentration:
Two different temperature water baths were created, one at 65-70oC, the other ice, and set aside for Part B.
20 mL of potassium thiocyanate solution were poured into a petri dish. The initial color and all subsequent observations were recorded in the data table.
Three drops of iron (III) nitrate were added to different spots in the petri dish, and the resulting solution was swirled until the color was consistent.
Approximately ½ pea-sized sample of potassium …show more content…
thiocyanate crystals was added to one spot. After 30 seconds, the solution was mixed.
Approximately a ½ pea-sized sample of potassium nitrate crystals was added to one spot in the petri dish. After 30 seconds, this solution was again mixed.
About a ¼ pea-sized sample of sodium phosphate monobasic crystals were added to one spot in the petri dish. After 60 seconds, this solution was mixed.
One drop of iron (III) nitrate solution was added to the side of the petri dish, while a pea-sized amount of potassium thiocyanate crystals was added to a different spot. After 30 seconds, the solution was swirled to ensure the crystals fully dissolved and this final solution was saved for use in Part B.
Part B: Effect of Temperature:
The solution saved from Part A was divided evenly into two test tubes labelled 'A' and 'B'. Test tube A was kept as the control. Test tube B was placed into an ice water bath for three to five minutes and then compared to the control.
Test tube B was then placed into a hot water bath for two to three minutes and again compared to the control.
**
Activity A: Acid-Base Indicator Equilibrium
Approximately 2 ml of deionized water was added into a test tube with 5 drops of 0.04 % bromthymol blue.
Four drops of 0.1 M hydrochloric acid was added to the solution and mixed.
Four drops of 0.1 M sodium hydroxide was added to the solution and mixed.
After solution appeared to change back to original conditions.
Activity B: Formation of a copper complex ion.
5 mL of 0.2 M copper (II) sulfate was added to a test tube.
One Drop of ammonium hydroxide was added to 5 mL of copper (II) sulfate
Another drop of ammonium hydroxide was added to the solution
Two Drops of hydrochloric acid was added to the solution
Two Drops of ammonium hydroxide was added to the solution
Four drops of hydrochloric acid was added to the solution
Another 2 drops of hydrochloric was added to the solution
Activity C: Formation of a Cobalt Complex Ion.
2 mL of the cobalt chloride solution was added to three separate test tubes (A, B, and C).
1 mL of silver nitrate (milky white color) was added in test tube A
Three gains of calcium chloride was added to test tube B
1 mL of Hydrochloric Acid was added to test tube C
Activity D: Solubility of Carbon Dioxide:
Approximately 10 mL of fresh seltzer water has mixed with 20 drops of 0.04 % bromcresol green indicator. The initial color was compared to a pH chart.
The solution was drawn up into a syringe, the excess air squeezed out, and the syringe capped.
A vacuum was generated by pulling out the syringe, and the solution was shaken.
The solution was then compared against a color coded pH chart to determine any change.
Activity E: Solubility of Magnesium Hydroxide
10 mL of milk of magnesia was added to 50 mL or deionized water in a beaker with 5 - 10 drops of universal indicator solution. This mixture was placed on a magnetic stirrer, to ensure consistent …show more content…
mixing.
Eight drops of indicator fluid is added to 10 mL of milk of magnesia
The solution was placed in
SAFETY CONSIDERATIONS:
Cobalt chloride solution is moderately toxic by ingestion. Iron (III) nitrate solution may be a skin and body tissue irritant. Concentrated ammonia (ammonium hydroxide) solution is severely corrosive and toxic by inhalation and ingestion. Work with concentrated ammonium hydroxide only in a fume hood. Hydrochloric acid solution is toxic by ingestion and inhalation and is corrosive to skin and eyes. Dilute hydrochloric acid and sodium hydroxide solutions are skin and eye irritants. Potassium thiocyanate is toxic by ingestion and emits a toxic gas if strongly heated - do not heat this solution and do not add acid. Sodium phosphate monobasic is moderately toxic by ingestion. Avoid contact of all chemicals with eyes and skin. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.
Waste disposal followed as indicated by the teacher.
PRE-LAB QUESTIONS:
Explain why the solubility of iodine in water increases as the concentration of potassium iodide increases.
Adding potassium iodide stresses the equation in favor of one side. In order to un-stress or relief the equation, the concentration of iodide must increase in order to maintain equilibrium.
Equation: N2 (g) + O2 (g) + 180kJ ⇌ 2NO(g)
Explain why concentration of NO increases as Temperature increases.
As temperature increases the equation would shift to the right, thus
Predict whether the concentration of NO at equilibrium should increase as the reaction takes place at higher pressures.
Both sides of the equation have equal amounts of gas moles meaning when a pressures are increasing nothing should happen to the concentration of NO.
DATA TABLES: ****
Part A: Effect of Concentration
Procedure:
Observation
Initial 20mL of potassium thiocyanate solution
A light orange brown clear liquid
½ pea-sized potassium thiocyante crystal was added
No reaction/No color change
Sodium phosphate was added and mixed into the solution ( ½ pea-sized)
The colors changed from red to orange to a peach
Addition of Iron (III) was placed at the brim of the solution
The solution turned blood red and created an 'eyeball effect' (blood red sitting on top of a lighter color)
Addition of potassium thiocyanate was placed at the brim of the petri dish
Slow change from an orangey red to a burnt orange color
Part B: Effect of Temperature
Procedure:
Observation
The solution was split into two test tubes (A and B)
A burnt orange color
Test tube A was placed in an ice water bath for 3 minutes
The solution changed from its previous burnt orange to a reddish brown color
Test tube B was placed in a hot water bath (70°C)
The solution began to take on a much lighter orange color
Activity A: Acid-Base Indicator Equilibrium
Procedure:
Observation
Initial 2 mL of deionized water
The color is clear
Five drops of brothymol blue (.04 %) is added to 2 mL of deionized water
The color shifted from clear to yellow
Four drops of hydrochloric acid is added to the solution
The color shifted from yellow to blue green then quickly reverts back to its previous stage yellow
Four drops of sodium hydroxide is added to the solution
The color shifts from yellow to blue and stays in this stage of blue
Activity B: Formation of a copper complex ion
Procedure:
Observations
5 mL of copper (II) sulfate was added to a test tube
A clear blue
One drop of ammonium hydroxide was added to 5 mL of copper sulfate
The color shifted from clear blue to dark blue
Another drop of ammonium hydroxide was added to the solution and mixed thoroughly
The solution changes to a lighter sky blue
Two drops of hydrochloric acid is added to the solution and mixed
The color shifted back to its initial blue color
Two drops of ammonium hydroxide was added to the solution and mixed
The color shifted to a indigo on the top and the initial blue still on the bottom
Four drops of hydrochloric acid was added to the solution and mixed
The color shifted to a light blue color
Another two drops of hydrochloric acid is added to the solution and mixed
Fragments were formed and blue ring are reflected at the top of the test tube
Activity C: Formation of a Cobalt Complex Ion.
Procedure:
Observations
2 mL of cobalt chloride was added into 3 test tubes. The test tubes were labeled A, B, and C
The initial color was light pink
1 mL of silver nitrate was added in test tube A
The milky white silver nitrate made the solution turn a light pale pink color with white at the bottom of the tube
Three grains of calcium chloride was added to test tube B.
The grains settled at the bottom and turned the bottom of the solution blue as they began to dissolve
1 mL of hydrochloric acid was added to test tube C.
The solution turned clear blue with a blue ring at the top of the test tube
Activity D: Solubility of Carbon Dioxide
Procedure:
Observations
Added 10 mL of seltzer water to 50 mL beaker
The initial color was clear
Added twenty drops of .04% bromcresol green to the 50 mL breaker
The color shfited to turquoise (4.5pH)
We drew up 10 mL of the solution with a 30 mL syringe (sealed) and shook its contents
The solution moved to a blue color (5.0pH)
Activity E: Solubility of Magnesium Hydroxide
Procedure:
Observations
50 mL of distilled water was added to a 250 mL breaker
The initial color was clear
10 mL of milk of magnesia solution was added to 50 mL of distilled water
The color changed to a milky white
Eight drops of indicator fluid was added to the solution
The color shifted to a light purple color
1 mL hydrochloric acid was added to the solution
The solution changed colors rapidly from pink to yellow to green then back to the light purple
Another mL of hydrochloric acid was added to the solution
The solution changed colors rapidly again from pink to yellow to green to teal to blue then back to purple
One more mL of hydrochloric acid was added to the solution
The solution changed colors rapidly once more from pink to green to teal to blue and slowly turned back to purple
CONCLUSIONS:
Overall, the application of Le Châtelier's Principle explained the chemistry behind the color changes taking place in the experiment.
When adding a reactant into the solution, the volume of the solution (and as a result the concentration of the reactants in the solution) was immediately changed. Using Le Châtelier's Principle we were able to predict which side the reaction would be shifted. The delineation between the reactant and products colors allowed for this. Changes in equilibrium could easily be observed though visible, qualitative color changes. These color changes were indications of Le Châtelier's Principle, which states that if a system is subject to stress, the system will react to remove the stress. To remove the stress, reactions either shift to the right and form more products, or to the left adding more reactants to the
solution.
ERROR ANALYSIS AND SUGGESTIONS FOR IMPROVEMENT:
Due to limitations of time on first day of experimenting, my colleagues and I were unable to maintain a control group for Part B of the Lab.
There were also errors in the process of Activity B where our solutions weren't mixed well enough to get thoroughly consistent colors.
(September 11 - 15, 2014)
**The purpose of this experiment was to visually observe the effects of how changing certain aspects of the reaction affected the observed equilibrium.
PROCEDURE:
Introductory activity
Part A: Effect of Concentration:
Two different temperature water baths were created, one at 65-70oC, the other ice, and set aside for Part B.
20 mL of potassium thiocyanate solution were poured into a petri dish. The initial color and all subsequent observations were recorded in the data table.
Three drops of iron (III) nitrate were added to different spots in the petri dish, and the resulting solution was swirled until the color was consistent.
Approximately ½ pea-sized sample of potassium …show more content…
thiocyanate crystals was added to one spot. After 30 seconds, the solution was mixed.
Approximately a ½ pea-sized sample of potassium nitrate crystals was added to one spot in the petri dish. After 30 seconds, this solution was again mixed.
About a ¼ pea-sized sample of sodium phosphate monobasic crystals were added to one spot in the petri dish. After 60 seconds, this solution was mixed.
One drop of iron (III) nitrate solution was added to the side of the petri dish, while a pea-sized amount of potassium thiocyanate crystals was added to a different spot. After 30 seconds, the solution was swirled to ensure the crystals fully dissolved and this final solution was saved for use in Part B.
Part B: Effect of Temperature:
The solution saved from Part A was divided evenly into two test tubes labelled 'A' and 'B'. Test tube A was kept as the control. Test tube B was placed into an ice water bath for three to five minutes and then compared to the control.
Test tube B was then placed into a hot water bath for two to three minutes and again compared to the control.
**
Activity A: Acid-Base Indicator Equilibrium
Approximately 2 ml of deionized water was added into a test tube with 5 drops of 0.04 % bromthymol blue.
Four drops of 0.1 M hydrochloric acid was added to the solution and mixed.
Four drops of 0.1 M sodium hydroxide was added to the solution and mixed.
After solution appeared to change back to original conditions.
Activity B: Formation of a copper complex ion.
5 mL of 0.2 M copper (II) sulfate was added to a test tube.
One Drop of ammonium hydroxide was added to 5 mL of copper (II) sulfate
Another drop of ammonium hydroxide was added to the solution
Two Drops of hydrochloric acid was added to the solution
Two Drops of ammonium hydroxide was added to the solution
Four drops of hydrochloric acid was added to the solution
Another 2 drops of hydrochloric was added to the solution
Activity C: Formation of a Cobalt Complex Ion.
2 mL of the cobalt chloride solution was added to three separate test tubes (A, B, and C).
1 mL of silver nitrate (milky white color) was added in test tube A
Three gains of calcium chloride was added to test tube B
1 mL of Hydrochloric Acid was added to test tube C
Activity D: Solubility of Carbon Dioxide:
Approximately 10 mL of fresh seltzer water has mixed with 20 drops of 0.04 % bromcresol green indicator. The initial color was compared to a pH chart.
The solution was drawn up into a syringe, the excess air squeezed out, and the syringe capped.
A vacuum was generated by pulling out the syringe, and the solution was shaken.
The solution was then compared against a color coded pH chart to determine any change.
Activity E: Solubility of Magnesium Hydroxide
10 mL of milk of magnesia was added to 50 mL or deionized water in a beaker with 5 - 10 drops of universal indicator solution. This mixture was placed on a magnetic stirrer, to ensure consistent …show more content…
mixing.
Eight drops of indicator fluid is added to 10 mL of milk of magnesia
The solution was placed in
SAFETY CONSIDERATIONS:
Cobalt chloride solution is moderately toxic by ingestion. Iron (III) nitrate solution may be a skin and body tissue irritant. Concentrated ammonia (ammonium hydroxide) solution is severely corrosive and toxic by inhalation and ingestion. Work with concentrated ammonium hydroxide only in a fume hood. Hydrochloric acid solution is toxic by ingestion and inhalation and is corrosive to skin and eyes. Dilute hydrochloric acid and sodium hydroxide solutions are skin and eye irritants. Potassium thiocyanate is toxic by ingestion and emits a toxic gas if strongly heated - do not heat this solution and do not add acid. Sodium phosphate monobasic is moderately toxic by ingestion. Avoid contact of all chemicals with eyes and skin. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.
Waste disposal followed as indicated by the teacher.
PRE-LAB QUESTIONS:
Explain why the solubility of iodine in water increases as the concentration of potassium iodide increases.
Adding potassium iodide stresses the equation in favor of one side. In order to un-stress or relief the equation, the concentration of iodide must increase in order to maintain equilibrium.
Equation: N2 (g) + O2 (g) + 180kJ ⇌ 2NO(g)
Explain why concentration of NO increases as Temperature increases.
As temperature increases the equation would shift to the right, thus
Predict whether the concentration of NO at equilibrium should increase as the reaction takes place at higher pressures.
Both sides of the equation have equal amounts of gas moles meaning when a pressures are increasing nothing should happen to the concentration of NO.
DATA TABLES: ****
Part A: Effect of Concentration
Procedure:
Observation
Initial 20mL of potassium thiocyanate solution
A light orange brown clear liquid
½ pea-sized potassium thiocyante crystal was added
No reaction/No color change
Sodium phosphate was added and mixed into the solution ( ½ pea-sized)
The colors changed from red to orange to a peach
Addition of Iron (III) was placed at the brim of the solution
The solution turned blood red and created an 'eyeball effect' (blood red sitting on top of a lighter color)
Addition of potassium thiocyanate was placed at the brim of the petri dish
Slow change from an orangey red to a burnt orange color
Part B: Effect of Temperature
Procedure:
Observation
The solution was split into two test tubes (A and B)
A burnt orange color
Test tube A was placed in an ice water bath for 3 minutes
The solution changed from its previous burnt orange to a reddish brown color
Test tube B was placed in a hot water bath (70°C)
The solution began to take on a much lighter orange color
Activity A: Acid-Base Indicator Equilibrium
Procedure:
Observation
Initial 2 mL of deionized water
The color is clear
Five drops of brothymol blue (.04 %) is added to 2 mL of deionized water
The color shifted from clear to yellow
Four drops of hydrochloric acid is added to the solution
The color shifted from yellow to blue green then quickly reverts back to its previous stage yellow
Four drops of sodium hydroxide is added to the solution
The color shifts from yellow to blue and stays in this stage of blue
Activity B: Formation of a copper complex ion
Procedure:
Observations
5 mL of copper (II) sulfate was added to a test tube
A clear blue
One drop of ammonium hydroxide was added to 5 mL of copper sulfate
The color shifted from clear blue to dark blue
Another drop of ammonium hydroxide was added to the solution and mixed thoroughly
The solution changes to a lighter sky blue
Two drops of hydrochloric acid is added to the solution and mixed
The color shifted back to its initial blue color
Two drops of ammonium hydroxide was added to the solution and mixed
The color shifted to a indigo on the top and the initial blue still on the bottom
Four drops of hydrochloric acid was added to the solution and mixed
The color shifted to a light blue color
Another two drops of hydrochloric acid is added to the solution and mixed
Fragments were formed and blue ring are reflected at the top of the test tube
Activity C: Formation of a Cobalt Complex Ion.
Procedure:
Observations
2 mL of cobalt chloride was added into 3 test tubes. The test tubes were labeled A, B, and C
The initial color was light pink
1 mL of silver nitrate was added in test tube A
The milky white silver nitrate made the solution turn a light pale pink color with white at the bottom of the tube
Three grains of calcium chloride was added to test tube B.
The grains settled at the bottom and turned the bottom of the solution blue as they began to dissolve
1 mL of hydrochloric acid was added to test tube C.
The solution turned clear blue with a blue ring at the top of the test tube
Activity D: Solubility of Carbon Dioxide
Procedure:
Observations
Added 10 mL of seltzer water to 50 mL beaker
The initial color was clear
Added twenty drops of .04% bromcresol green to the 50 mL breaker
The color shfited to turquoise (4.5pH)
We drew up 10 mL of the solution with a 30 mL syringe (sealed) and shook its contents
The solution moved to a blue color (5.0pH)
Activity E: Solubility of Magnesium Hydroxide
Procedure:
Observations
50 mL of distilled water was added to a 250 mL breaker
The initial color was clear
10 mL of milk of magnesia solution was added to 50 mL of distilled water
The color changed to a milky white
Eight drops of indicator fluid was added to the solution
The color shifted to a light purple color
1 mL hydrochloric acid was added to the solution
The solution changed colors rapidly from pink to yellow to green then back to the light purple
Another mL of hydrochloric acid was added to the solution
The solution changed colors rapidly again from pink to yellow to green to teal to blue then back to purple
One more mL of hydrochloric acid was added to the solution
The solution changed colors rapidly once more from pink to green to teal to blue and slowly turned back to purple
CONCLUSIONS:
Overall, the application of Le Châtelier's Principle explained the chemistry behind the color changes taking place in the experiment.
When adding a reactant into the solution, the volume of the solution (and as a result the concentration of the reactants in the solution) was immediately changed. Using Le Châtelier's Principle we were able to predict which side the reaction would be shifted. The delineation between the reactant and products colors allowed for this. Changes in equilibrium could easily be observed though visible, qualitative color changes. These color changes were indications of Le Châtelier's Principle, which states that if a system is subject to stress, the system will react to remove the stress. To remove the stress, reactions either shift to the right and form more products, or to the left adding more reactants to the
solution.
ERROR ANALYSIS AND SUGGESTIONS FOR IMPROVEMENT:
Due to limitations of time on first day of experimenting, my colleagues and I were unable to maintain a control group for Part B of the Lab.
There were also errors in the process of Activity B where our solutions weren't mixed well enough to get thoroughly consistent colors.