INSTRUCTIONS 1. 8. Observe how the colour changes. OBSERVATIONS Design and construct tables to record the colours observed. The solution turned blue. Continue to drop water slowly until all the crystals have fallen or dissolved into the flask, then finish filling the flask to the 25 mL graduation, and shake. CoCl2 is used in hygrometers due to its color-changing abilities. If you add water, the equilibrium will shift to the left and the color will be pink.If you add #"HCl"#, which will increase the concentration of #"Cl"^(-)"# ions, the equilibrium will shift to the right and the color will be blue.. With a small stirring rod, stir wells 3, 7, and 11; rinse and dry the rod after each use. For an experiment involving dilution with water, a solution that is blue at room temperature is needed. Add concentrated HCl dropwise until a distinct color change occurs. The ion Co2+ (aq) is pink. At each of steps 5 to 9, all observed changes of colour should be recorded. 2. 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If concentrations of ions are changed by addition of solid cobalt(II) chloride, concentrated hydrochloric acid, or water, then predictable changes in colour are likely to be observed. with respect to the effect of an increase in the concentration of chloride ions upon the position of the equilibrium? Five drops of CoCl2 was added to each of the 24 wells in the well plate. Measure 12 mL of concentrated hydrochloric acid in a graduated cylinder, then pour it slowly over the solid cobalt chloride in the funnel, so that the crystals dissolve and fall into the flask. Color after the addition of H2O is clear pink. At relatively low concentrations of chloride, the equilibrium lies far to the right, and the solution is pink. A certain lead ore contains the compound PbCO3. As a greater concentration of HCl was added to the CoCl2 solutions, the color changed. Six drops were added to column 3. Record the final pattern of colours seen in the wells 1 to 12. The +2 state is more common. (with respect to the effect of an increase in the concentration of cobalt(II) ions upon the position of the equilibrium. (Well 1 should contain a sample of the initial solution, as a control.) Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula CoCl 2. The solution should be dark blue-purple in colour. Account for the changes you observe for the cobalt solutions in … Table two: effects of addition of a drop of concentrated HCl to solutions 3, 7 and 11. 5. Stir each sample gently with a small glass rod. THE COBALT CHLORIDE EQUILIBRIUM. Chem help, chemical bonds and wavelength? The ion Co 2+ (aq) is pink. E. [Co(H2O)6] 2+, [CoCl4] 2– Equilibrium (Temperature Effect) 1. I went to a Thanksgiving dinner with over 100 guests. For example, if a solution that is pink (equilibrium to the right) increases in its concentration of either cobalt(II) or of chloride, then its colour should change towards blue. If such a solution is diluted just sufficiently for a distinct change towards pink to be observed, then it may be possible to reverse the change and restore blueness by addition of either concentrated hydrochloric acid or solid cobalt(II) chloride. I have a few question about an equilibrium lab we performed. The chief was seen coughing and not wearing a mask. 4) blue, because the hydrochloric acid reacts with the water to form H3O+, thus reducing the amount of water on the right side of the equilibrium equation. Predict and justify the color of the solution after concentrated hydrocloric acid is added. 5. 4. 9. PLANNING By trial and error, it is known that a solution in which [Co2+ (aq)] = 0.5M and [Cl-(aq)] = 5M will be blue at room temperature but pink if refrigerated. BACKGROUND INFORMATION The element cobalt can form compounds in two different oxidation states, +2 and +3. Predict and justify the color of the solution after concentrated hydrocloric acid is added. The color began to shift from being pink to slowly becoming more blue. It can help calculate the levels of humidity in the air. I almost know for a fact that it turns blue not sure of the exact reason behind it though, - if the temperature is very low : CoCl2.6H2O + HCl --> no reaction, color stays the same (but the equilibrium change), - room temperature : CoCl2.6H2O + HCl --> (CoCl4)2- (blue). To each of wells 3, 7 and 11, add one drop of concentrated hydrochloric acid. Account for the changes you observe for the cobalt solutions in … Join Yahoo Answers and get 100 points today. Place about 10 drops of 1 M CoCl2 in a clean test tube. Other compounds of cobalt(II), which include both anhydrous Co 2+ and complex ions, are commonly blue.. (This amount should be sufficient for about six students, working individually.). How can any changes of colour observed in the solutions as a result of stirring be explained? Likewise, any other stress applied to the equilibrium will produce a color change in the solution. 3. One reliable source quotes it vaguely as a change in coordination of the metal ion. The oxygens which were originally attached to the cobalt are still attached in the neutral complex. 6. The color began to shift from being pink to slowly becoming more blue. with respect to the effect of dilution with water upon the position of the equilibrium? At lower temperatures, the equilibrium tends to lie to the right, that is, to be more pink; at higher temperatures, it lies to the left and appears more blue. 10. A sample of the ore weighing 4.301 g was treated with nitric acid, which dissolved the PbCO3. Still have questions? 7. Variations, comparisons, or trends of colour should also be recorded.). Weigh 3.00 g of solid cobalt(II) chloride and put it in a small funnel placed in the mouth of a 25 mL volumetric flask. Predict and justify the color of the solution after concentrated hydrocloric acid is added. Five drops of CoCl2 are dropped in each well. 4. 2. MATERIALS REQUIRED To make 25 mL of solution in which [Co2+ (aq)] = 0.5M and [Cl-(aq)] = 5M: balance, CoCl2.6H2O = 3.0 g, concentrated HCl = 12.0 mL, 25 mL volumetric flask, 25 mL graduated cylinder, balance, small funnel, deionised water, dropper. It is a sky blue crystalline solid. The color change is recorded. Four drops were added into column 2. Using a pasteur pipette, add one drop of water to each of wells 2, 3 and 4, two drops of water to each of wells 6, 7 and 8, and three drops of water to each of wells 10, 11 and 12. Two drops of HCl are added to each well in column 1; four in column 2, six in column 3, eight in column 4, and ten in column 5. Color after the addition of HCl is dark blue. Color of CoCl2 is clear pink. Effect of concentrated HCl. To test effects of changes of concentration of solutes: white glazed tile, white glazed well-plate, 1 mL graduated pipette with filler bulb (or automatic delivery pipette), pasteur pipettes, small spatula, four small glass stirring rods, small stock supplies of concentrated hydrochloric acid and of solid cobalt(II) chloride, deionised water. Place ~10 drops of 1.0 M CoCl2 in a 75-mm test tube.18 Add drops of conc HCl (Caution: Avoid inhalation and skin contact) until a color change occurs.19 Slowly add water to the system and stir. What does heat do? The color that forms is from the complex ion [Co(H:0)] 2. Vials of CoCl2, HCl, H2O, and AgNO3 was obtained. Eight drops were added to column 4. As a greater concentration of HCl was added to the CoCl2 solutions, the color changed. which makes you more jittery coffee or tea? Slowly add H:0 to the test tube while mixing until a color change is detected. You are given an aqueous solution of cobalt chloride, which is pink. With a small stirring rod, stir wells 4, 8, and 12.; rinse and dry the rod after each use. 6. Other compounds of cobalt(II), which include both anhydrous Co2+ and complex ions, are commonly blue. 1) pink, because there will be more ions present from the left side of the equilibrium equation, 2) pink, because hydrochloric acid is not in the equilibrium equation, 3) blue, because the addition of more chloride ions will cause more of the [CoCl4]2-(aq) to form. If an aqueous solution contains both cobalt(II) and chloride ions, the blue ion CoCl 4 2 … Color after the addition of H2O is clear pink. To show the reversibility of the reaction with changing temperature, place the flask, or a sample of solution taken from the flask into a small closed tube or bottle, into the coldest part of a refrigerator. If an aqueous solution contains both cobalt(II) and chloride ions, the blue ion CoCl42- forms, in equilibrium with the pink Co2+ (aq) ion. The color change is recorded and a photo is taken. 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