Question

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Lab 8: Studying Chemical Equilibria and Applying Le Chatelier's Principle Using Microscale Techniques 4. A student is studying the equilibrium described by Equation 19 heat + Coso, . 7 H2O(s, pink) + 7SOCIeO-Coso,(s, blue) + 7S02(g) + 14HC?(g) (Eq.19) Using microscale techniques and working in a fume hood, the student mixes pink CoSO4.7H2O with SOCIz and heats the mixture in a covered container. The solid turns blue. The student removes the cover from the container and stirs the blue solid. After replacing the cover, the student cools the mixture, but observes no color change. Briefly explain the basis for the student's observations.

Answer 1

Sol:-

Equilibrium always maintain in a close container.

CuSO4.7H2O solid which is pink in colour lies in reactants side.on heating this pink solid a blue colour solid i.e CuSO4 is formed in products and after some time equilibrium is maintained in a close container.

Heating of pink solid is a endothermic reaction i.e for this reaction value of ?H = +ve.

Now , after removing the cover equilibrium will shifts in forward direction because SO2(g) and HCl(g) starts to escape from reaction mixture and therefore blue solid CuSO4 appears.

But , after cooling this hot mixture , equilibrium shifts to backwards direction ( because reaction is endothermic )and therefore now blue solid converted back to form pink solid which lies in reactants side and hence no colour change on cooling or lowering in temperature.

This all is accordance with Le Chatelier's principle which states that if any kind of change in pressure, temperature and concentration is imposed on the system in equilibrium , then equilibrium shifts in a direction that tends to undo the effect of the change imposed.