10 Questions
What is the purpose of adding HCl to the reaction mixture in Part A?
To shift the equilibrium to the left
What happens to the equilibrium mixture when it is exposed to hot water in Part B?
The solution becomes lighter in color
What is the effect of adding potassium thiocyanate (KSCN) solution to the reaction mixture in Part A?
The equilibrium shifts to the right
What is the conclusion of the experiment regarding the effect of temperature on the equilibrium reaction?
Adding heat favors the direction of the endothermic reaction, and removing heat favors the direction of the exothermic reaction
What is the role of iron(III) chloride (FeCl₃) in the experiment?
It provides the source of Fe³⁺ ions
What is the significance of the color change observed in the experiment?
The color change indicates a shift in the equilibrium reaction. A red color indicates the formation of the complex ion FeCNS²⁺, while a yellow color indicates the presence of Fe³⁺ ions.
How does the addition of HCl affect the equilibrium reaction in Part A?
The addition of HCl causes the equilibrium to shift to the left, as the CL⁻ ions are absorbed.
What is the effect of temperature on the equilibrium reaction, as observed in Part B?
The reaction is endothermic, as the equilibrium shifts to the left at higher temperatures, and exothermic, as the equilibrium shifts to the right at lower temperatures.
What is the purpose of using iron(III) chloride and potassium thiocyanate in the experiment?
Iron(III) chloride provides Fe³⁺ ions, and potassium thiocyanate provides CNS⁻ ions, which react to form the complex ion FeCNS²⁺.
What is the significance of Le Chatelier's principle in the context of this experiment?
Le Chatelier's principle states that a system at equilibrium will adjust to counteract changes to the equilibrium conditions, such as concentration and temperature.
Study Notes
- The experiment demonstrates the Chatelier's principle by studying the effects of concentration and temperature changes on the reaction Fe³⁺ + CNS⁻ ⇌ FeCNS²⁺.
- The reaction involves iron(III) chloride (FeCl₃) as the source of Fe³⁺ ions and potassium thiocyanate (KSCN) as the source of CNS⁻ ions.
- Fe³⁺ ions are yellow, and CNS⁻ ions are colorless, but when combined, they form a complex ion, FeCNS²⁺, which is red.
- In Part A, the effect of concentration on the equilibrium reaction is investigated by adding HCl and KSCN solutions to the reaction mixture.
- Adding HCl causes the red color to disappear, shifting the equilibrium to the left, as the CL⁻ ions are absorbed.
- Adding KSCN solution causes the solution to become red again, shifting the equilibrium to the right, as the CNS⁻ ions are absorbed.
- In Part B, the effect of temperature on the equilibrium reaction is investigated by diluting the solutions and exposing them to different temperatures (hot water, ice, and room temperature).
- The red color becomes lighter in the hot water test tube, indicating a shift to the left (endothermic reaction), and the yellow color appears.
- The equilibrium mixture becomes more red in the ice test tube, indicating a shift to the right (exothermic reaction), but this is difficult to detect.
- The experiment concludes that adding heat favors the direction of the endothermic reaction, and removing heat favors the direction of the exothermic reaction.
This quiz explores the effects of concentration and temperature changes on the equilibrium reaction Fe³⁺ + CNS⁻ ⇌ FeCNS²⁺, demonstrating Chatelier's principle. It investigates the reaction's response to adding HCl and KSCN solutions, and exposing the solutions to different temperatures. The quiz concludes that heat favors the endothermic reaction, while removing heat favors the exothermic reaction.
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