Chemical Equilibrium - Pre-lab quiz. Please help. 1. How will you be able to tel

Question

Chemical Equilibrium - Pre-lab quiz. Please help.

1. How will you be able to tell which way the equilibrium is shifting in the Cr2O72-/CrO42- equilibrium system?

2. According to Le Chatelier’s Principle, which way will an equilibrium shift (left or right) when heat is added if the reaction in the forward direction is exothermic?

3. In an undisturbed equilibrium system, why do the concentrations of the products and reactants remain constant?

4. In an equilibrium system involving Co(H2/O)62+ and NCS-, how will you decrease the concentration of NCS- in the mixture?

5. What should you do with the leftover reagents at the end of the experiment?

Explanation / Answer

1. Cr2O7^2- is orange in color whereas, CrO4^2- gives a yellow color. Thus by monitoring he color change of the solution, one may analyze which direction is the reaction proceeds.

2. For an exothermic reaction, according to LeChatellier's principle addition of heat would reverse the reaction equilibrium. This is to bring the temperature down of the reaction system.

3. The equilibrium state is when the reactant and products are in equilibrium with each other. The state is a constant known as reaction constant Kc or Keq, equilibrium constant.

4. To decrease the concentration of NCS-, the addition of heat would force the reaction to go in the forward direction and thus reduce NCS- concentration and formation of complex would occur.

5. The leftover reagent can be quenched at the end of the reaction and washed off.

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