LeChatelier\'s Principle: Chemical Equilibrium Introduction: The purpose of this
ID: 493147 • Letter: L
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LeChatelier's Principle: Chemical Equilibrium Introduction: The purpose of this lab is to observe the disturbance of various systems When a is disturbed, the equ brium will shift system at equilibrium equilibrium to minimize that disturbance. Part 1: Cobalt chloride hexahydrate Cocl -(aq) 6 H2O(l) Atco (H2O)62 (aq) 4 Cl (aq) obtain 4 large test tubes and label them A-D. Place a pea of (CoCl2-6 H20) in Each of size amount coba chloride hex the four test tubes. 3. Add 1 mL of distilled water to test tube A an r with a glass stirring rod. Place this test tube to the side. This solution will be your control. Write the color of your control solution in Table 1. Set it aside. 5. Carefully add 3 mL of concentrated HCI to test tub B C. and D tir the solution with a glass stirring rod. Write the color of test tube B (CoC 6 est tube Baside as a control solution for the color of CoCl4 until they each reach an intermediate Add distilled water dropwise to test tul color between test tube A and B. s Add a full scoopula of solid um chloride to test tube C and stir with a glass stirring rod. Write the color of your solution in Table Add a 1 mL of 0.10 M AgNOs solution to the bottom of the solution in test tube C. Wite the color of your solution in Table 1. le. Place test tube D in a hot water bath at 80-850C for 2-3 minutes. Write the color of your solution in Table 1. Using a test-tube holder, remove the hottest tube from the hot water bath. Cool it briefly and then immerse it directly in an ice water bath for 2-3 minutes. Write the color of your solution in Table 1.Explanation / Answer
a) Cobalt (II) chloride hexahydrate (CoCl2- 6H2O)2+
There is a complex equilibrium between these two complexes.
[Co (H2O)6]2+ + 4Cl- <===>[CoCl4]2- + 6H2O
Aqueous cobalt(II) chloride solution has a pink color, because six water molecules surround one cobalt(II) ion, thus forming octahedral hexa aqua cobalt(II) complex, [CoCl2(H2O)6]2+.
When we increase the chloride ions concentration by adding concentrated HCl into the pink [Co(H2O)6]2+ solution, water molecules from the inner complex sphere are gradually displaced by chlorine. When chloride ions concentration is sufficiently high, all water molecules are displaced and blue tetrachlorocobaltate (II) complex is formed. This [CoCl4]2- complex has regular tetrahedron geometry.
According to the Le Chatelier’s principle, the equilibrium can be disturbed by changing chloride ion concentration. When we add hydrochloric acid, the equilibrium shifts to the right in order to consume extra chloride ions, and blue tetrachlorocobaltate (II) is formed. Contrary, by adding more water leads to formation of pink hexaaquacobalt (II) complex. Le Châtelier’s principle predicts that if energy is removed by cooling the system, the equilibrium tends to shift toward the aquocomplex, because a shift in the equilibrium to produce more aquocomplexes produces some energy.
b) Methyl orange-
IN- + H3O+ <======>HIN + H2O
Methyl orange is red in the HIn state, yellow-orange in the IN- state. According to the Le Chatelier’s principle if the H3O+ is greater methyl orange shifts to the HIN state. If OH- is greater methyl orange shifts to the IN- state.
c)
Mg(NO3)2(aq) + NaOH (aq) = Mg(OH)2 +2 NaNO3
If NaOH is added , this stresses the system, so in order to reduce the effect of the stress, the reaction shifts left to remove it. The formation of solid is occurs. If HCl is added, the system is stressed, so in order to reduce the effect of the stress, the removal of product reaction shifts right to remove it. The solid is dissolved.
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