Post-Laboratory Questions (Use the spaces provided for the answers and additiona
ID: 590919 • Letter: P
Question
Post-Laboratory Questions (Use the spaces provided for the answers and additional paper if necessary) 1·) A student doing in thi ended the study of the [CoCl4]2-ion / [Co(H2O)6 Son of magnesium on equilibrium. In one test tube, the student added sil Mg(OH)2 undergoes t ver nitrate (AgNO3) to a blue equilibrium mixture pre- pared from CoCl2. The reaction mixture became pink and cloudy, and a white precipitate settled out leaving a clear, pink solution. The student identified the pre- cipitate as silver chloride, AgCi ng the experiment in this module ex 2 The popular antacid, Milk of Magnesia,is a suspen- hydroxide, MglOH)2 In water, the reaction shown in Equation 9 Mg(OH)2(s, white) g (a) 2 OH (aq) Eq.9) (1) What would you observe if you added an acid to an equilibrium mixture containing Mg(OH)2 in water? (1) Briefly explain how these observations are consistent with Le Châtelier's principle (2) Write a chemical equation that accounts for the effect of the added acid. In a second test, the student placed a test tube contain- ing a pink equilibrium mixture in a hot-water bath. The solution turned blue. When the student removed the test tube from the hot-water bath and placed it in an ice-water bath, the solution turned pink. (2) lsthe forward reaction in the [CoC4 ion, [Co(H2O)6)2. ion equilibrium exothermic or endother- mic? (3) Briefly explain how your answer to (1) is cor sistent with Le Châtelier's principle. (3) Briefly explain how the student's observa tions support your answer to (2). (4) Write the net ionic equation for this equilib- rium, including heat.Explanation / Answer
Q1
First, let us state the Le Chatelier principle which deals with changes in an equilibrium:
The statement is as follows:
If any equilibrium is disturbed, that is, change in conditions such as P,T, concentration, partial pressure, etc.., the system will counterbalance such change in order to favour the system's equilbirium.
as we added AgCl, Cl- ions decrease, so more Co(H2O)6 must form CoCl4 complex, in order to counterbalance this loss
b)
2nd test:
pink + hot water --> blue
pink solution = Co(H2O6)-2
blue solutino = CoCl4
if the reaction turns blue when heated, then this msut be endothermic
heat + Co(H2O)6-2 + 2Cl- = CoCl4-
C)
this can eb suported mainly because of the color change
d)
Net ionic equilbirium:
Co(H2O)6+2 + 4Cl- + heat = CoCl4-2 + 6H2O