International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page EXPERIMENT CHEMICAL EQUILIBRIUM Student name: _ ID: _ OBJECTIVES To observe the effect of applying stresses on chemical systems at equilibrium T L C P INTRODUCTION A reversible reaction is at equilibrium when the rate of the forward reaction becomes equal to the rate of the backward reaction Reversible reaction: Forward reaction C+D A + B Backward reaction A reversible reaction at equilibrium can be disturbed if a stress is applied to it Stresses can be changes in concentration, temperature or pressure The composition of the reaction mixture will shift until equilibrium has been reestablished This is known as L C principle In this experiment, the effect of applying stresses to a variety of chemical systems at equilibrium will be observed and we also see if the results are L C rinciple EQUIPMENTS Name mL Beaker mL Beaker mL Cylinder Distilled water bottle Goggle(s) Quantity Name mL Pipette Stirring Rod Test tube Test tube holder Test tube rack Quantity NOTE: Please check the quality and quantity of your equipment before starting Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page CHEMICALS PART CHEMICALS 0.5M K2Cr2O4 Potassium Chromate Concentrated HCl Hydrochloric Acid 6M NaOH Sodium Hydroxide Methyl Violet (indicator) 6M HCl Hydrochloric Acid 6M NaOH Sodium Hydroxide 0.01M FeCl3 Iron(III) Chloride 0.01M KSCN Potassium Thiocyanate 6M NaOH Sodium Hydroxide VOLUME (mL) PART CHEMICALS VOLUME (mL) 0.1M AgNO3 Silver Nitrate 0.1M CaCl2 Calcium Chloride 0.1M Na2C2O4 Sodium Oxalate 0.1M H2C2O4 Oxalic Acid 6M HCl Hydrochloric Acid 6M NH4OH Ammonium Hydroxide 0.1M CoCl2 Cobalt(II) Chloride Concentrated HCl Hydrochloric Acid NOTE: DISPOSAL OF CHEMICALS The toxic chemicals will be gathered in TOXIC CONTAINERS In this experiment, they include: Cobalt ion (Co2+) Thiocyanide ion (SCN-) Other nontoxic wastes will be disposed to WASTE CONTAINERS Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page PROCEDURE Part 1: Acid/Base Equilibria Equilibrium system: #1 10 drops 0.5M K2CrO4 Observe the color CrO42- + 2H+ (aq) Cr2O72- + H2O (l) #2 10 drops 0.5M K2CrO4 #3 10 drops 0.5M K2CrO4 drops Concentrated HCl drops Concentrated HCl Observe the color Compare with #1 Observe the color Compare with #1 10 drops 6M NaOH Observe the color Compare with #2 Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page Part 2: Equilibria Of Acid/Base Indicators Equilibrium system: H(MV) (aq) + H2O(l) H3O+ (aq) + MV (aq) drops methyl violet 20mL distilled water DIVIDE EQUALLY #1 #2 Add wisely until no significant change DON T ADD TOO MUCH Observe the color Drop 6M HCl Observe the color change Add wisely until no significant change DON T ADD TOO MUCH Drop 6M NaOH Observe the color change Add wisely until no significant change DON T ADD TOO MUCH Drop 6M HCl Observe the color change Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page Part 3: Complex Ion Formation Equilibrium system: Fe3+(aq) + SCN(aq) Fe(SCN)]2+(aq) (Pale yellow) (Pure) (Red) 10mL 0.01M FeCl3 10mL 0.01M KSCN 50mL distilled water DIVIDE EQUALLY #1 Observe the color (control tube) #2 #3 2mL 2mL 0.01M FeCl3 0.01M KSCN #4 #5 #6 10 drops 6M NaOH Cool (ice bath) Warm (hot bath) Compare the color with test tubes #1 #7 Drop 0.1M AgNO3 Drop until the color disappears Observe the color change CHEMICAL WASTES: Please dispose tubes containing thiocyanide ion (SCN-) to the TOXIC CONTAINER Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page Part 4: Equilibria Of Precipitation Reactions Equilibrium system: #1 Observe the color (control tube) Ca2+ (aq) + C2O42 (aq) CaC2O4 (s) 5mL 0.1M CaCl2 1mL 0.1M Na2C2O4 #2 5mL 0.1M CaCl2 1mL 0.1M H2C2O4 Observe the color Compare with #1 10 drops 6M HCl Observe the color change 10 drops 6M NH4OH Observe the color change Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page Part 5: Temperature Effects On Equilibria Equilibrium System: Co(H2O)62+ (aq) + 4Cl (aq) (CoCl4)2 (aq) + 6H2O (l) 3mL 0.1M CoCl2 Add conc HCl drop-by-drop #1 #2 STOP when solution turns to purple-violet DO AGAIN if deep blue appears (indicating too much Cl- added) #3 Room temperature Warm (hot water bath) Cool (ice bath) Observe the color (control tube) Observe the color Compare with #1 Observe the color Compare with #1 Cool (ice bath) Warm (hot water bath) Observe the color Compare with #1 Observe the color Compare with #1 CHEMICAL WASTES: Please dispose tubes containing cobalt ion (Co2+) to the TOXIC CONTAINER Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc International University, Vietnam National University - HCMC GENERAL CHEMISTRY LABORATORY Page REFERENCES [1] Experiments in General Chemistry: Inquiry and Skill building (Brooks/Cole Laboratory Series for General Chemistry) 2008 - Vickie Williamson (Author), Larry Peck, ISBN10:049555300X | ISBN-13: 978-0495553007 [2] Introduction to Chemical Principles: A Laboratory Approach (Brooks/Cole Laboratory Series for Introductory Chemistry) 7Ed (2009) - Susan A Weiner, Blaine Harrison, ISBN-10: 0495114790 | ISBN-13: 978-0495114796 [3] Laboratory Experiments for General, Organic and Biochemistry (Brooks/Cole Laboratory Series for General Chemistry) 4th Ed () - Frederick A Bettelheim (Author) All the source of documents are updated to March 02nd, 2017 ACKNOWLEDGEMENT This Lab manual was updated by Ms Ngo Hoan My and the Lab Manual Team*, and subsequently revised by MSc Le Nguyen Thien Phuc The earlier versions of this Lab manual were made by Assoc Prof Huynh Kim Lam, MSc Le Nguyen Thien Phuc, MSc Nguyen Tuong Linh and Ms Tran Thi Khanh Linh * Lab Manual Team: + Ms Ngo Hoan My + Ms Dang Hoai Bao Tran + Ms Le Pham Nguyet Thuong + Mr Nguyen Duy Hung + Ms Nguyen Ha Yen Last updated: 14/09/2017 by Lab Manual Team_ International University HCMC-VNU Revised by Assoc Prof Huynh Kim Lam and MSc Le Nguyen Thien Phuc ... test tubes #1 #7 Drop 0.1M AgNO3 Drop until the color disappears Observe the color change CHEMICAL WASTES: Please dispose tubes containing thiocyanide ion (SCN-) to the TOXIC CONTAINER Last updated:... Team*, and subsequently revised by MSc Le Nguyen Thien Phuc The earlier versions of this Lab manual were made by Assoc Prof Huynh Kim Lam, MSc Le Nguyen Thien Phuc, MSc Nguyen Tuong Linh and Ms Tran... chemicals will be gathered in TOXIC CONTAINERS In this experiment, they include: Cobalt ion (Co2+) Thiocyanide ion (SCN-) Other nontoxic wastes will be disposed to WASTE CONTAINERS Last updated: