Chem Lab 19A
Lab 19A Answers:
1) If we increase the molarity of NaOH from 0.1M to 0.2M, it will actually take less number of drops in order to change the color of the solution. This is because the more concentrated a substance is, less of the substance is needed to cause an equilibrium shift.
2) When you add 6.0M NaOH into the iron (III) thiocyanate ion equilibrium system, the concentration of Fe3+ ion decreases. This causes the equilibrium system to shift to the left (reactant) side. This is why the solution becomes lighter yellow. Fe(OH)3 is also formed during the experiment.
3) If the hydrated cobalt (II) ion complex was refrigerated, the temperature would decrease. Since this is an endothermic reaction a decrease in temperature will actually cause the equilibrium system to move to the left, favouring the reactants. When the reactants are favoured, the color of the solution will get lighter and change to pink/light red.
4) According to the following equilibrium equation:
Co(H2O)62+ (aq.) + 2Cl- (aq.) + energy ↔ Co(H2O)4Cl2 (aq.) + 2H2O (l)
In this equation, energy is on the reaction side (endothermic reaction) because when we added more heat (increased the temperature) into the solution, the solution changed colour from light pink to purple. This showed us that the equilibrium moved to the right (product) side. This is why temperature has to be on the reactants side (endothermic) in order for this shift to be possible.
5) If you add NaCl into the hydrated Cobalt (II) ion equilibrium, the concentration of the chloride ions would increase and some sodium ions would be formed. Because of this, the concentration of reactants increases which causes the equilibrium system to move to the right (products) side. Therefore, the solution turns purple.
6) Cr2O72- + 2OH- ↔ 2CrO42- + H2O
9) In step 7, there was HCL added prior to the addition of barium nitrate and this caused the reaction to shift right causing the production of additional dichromate. This meant there was a
1) If we increase the molarity of NaOH from 0.1M to 0.2M, it will actually take less number of drops in order to change the color of the solution. This is because the more concentrated a substance is, less of the substance is needed to cause an equilibrium shift.
2) When you add 6.0M NaOH into the iron (III) thiocyanate ion equilibrium system, the concentration of Fe3+ ion decreases. This causes the equilibrium system to shift to the left (reactant) side. This is why the solution becomes lighter yellow. Fe(OH)3 is also formed during the experiment.
3) If the hydrated cobalt (II) ion complex was refrigerated, the temperature would decrease. Since this is an endothermic reaction a decrease in temperature will actually cause the equilibrium system to move to the left, favouring the reactants. When the reactants are favoured, the color of the solution will get lighter and change to pink/light red.
4) According to the following equilibrium equation:
Co(H2O)62+ (aq.) + 2Cl- (aq.) + energy ↔ Co(H2O)4Cl2 (aq.) + 2H2O (l)
In this equation, energy is on the reaction side (endothermic reaction) because when we added more heat (increased the temperature) into the solution, the solution changed colour from light pink to purple. This showed us that the equilibrium moved to the right (product) side. This is why temperature has to be on the reactants side (endothermic) in order for this shift to be possible.
5) If you add NaCl into the hydrated Cobalt (II) ion equilibrium, the concentration of the chloride ions would increase and some sodium ions would be formed. Because of this, the concentration of reactants increases which causes the equilibrium system to move to the right (products) side. Therefore, the solution turns purple.
6) Cr2O72- + 2OH- ↔ 2CrO42- + H2O
9) In step 7, there was HCL added prior to the addition of barium nitrate and this caused the reaction to shift right causing the production of additional dichromate. This meant there was a