Investigating Chemical Equilibrium Essay

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Objectives 1. To recognize the macroscopic properties of five chemical systems at equilibrium 2. To observe shifts in equilibrium concentrations as stresses are applied to the systems. 3. To observe a shift in equilibrium concentrations associated with changes in temperature. 4. To explain the observations obtained by applying Le Chatelier’s principle. Materials Refer to page 209 of Heath Chemistry Laboratory Experiments. Procedure Refer to pages 209 – 211 of Heath Chemistry Laboratory Experiments. Data and Observations Part I: Equilibrium Involving Thymol Blue Table 1 Reagent Added | Stress (Ion Added) | Colour Observation | Direction of Equilibrium Shift | NaOH (Step 5) | OH⁻ | Green | Left |…show more content…
| Dark Blue Mixture | Light Blue Solution ppt. | Questions and Calculations 1) Since the [OH⁻] would double, half the required number of drops would be needed. 2) Adding OH⁻ would react with the Fe³⁺ in the system to form a precipitate Fe(OH)₃. This would decrease the [Fe³⁺] in the system. Equilibrium will shift left to counteract the change and the solution becomes lighter yellow in colour. 3) Cooling the contents decreases the amount of heat in the system. Equilibrium will shift to the left causing the solution to become light red. 4) Heating favours endothermic reactions. As the reactant “Co(H₂O)₆²⁺” was heated, the solution changed from light red to dark purple. This suggests that the equilibrium shifted right. Therefore, the forward reaction is endothermic. 5) Adding NaCl would increase [Cl⁻]. This will cause equilibrium to shift right and the solution would become dark purple. 6) 2 CrO₄²⁻ + 2 H⁺ ↔ Cr₂O₇ + H₂O 2 H₂O ↔ 2 H⁺ + 2 OH⁻ 2 Cr₂O₄²⁻ + H₂O ↔ Cr₂O₇²⁻ + 2 OH⁻ 7) If you add HCl, you are increasing the [H⁺] in the system. Equilibrium will shift right causing the colour change from yellow to orange. If you add NaOH, the OH⁻ will react with the H⁺ ions to form water. This causes a decrease in the [H⁺] in the system. Equilibrium will shift causing the colour change from orange to yellow. 8) Omit 9) Omit 10) When HCl was added, the H⁺ ions reacted with the NH₃ to form NH₄⁺. This causes the [NH₃] to
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