Question

Using the reaction seen below, describe the color change that would indicate a shift from orange at equilibrium. FeSCN^2+ - fe^3+ +scn^- (3 points) Red (Reverse) Pale Yellow (Forward) Removal of FeSCN2+ Removal of Fe3+ Addition of SCN−

Answer 1

In the equilibrium reaction between Fe³⁺ and SCN⁻ to form the complex ion FeSCN²⁺, the color change can indicate the direction of the shift in equilibrium.

1. **Normal State (Equilibrium)**: The solution is initially orange due to the presence of the FeSCN²⁺ complex.

2. **Color Change Indications**:
- **Forward Reaction (Shift Right)**: If SCN⁻ is added to the system, the equilibrium shifts to the right to form more FeSCN²⁺, resulting in an increase in the orange color.
- **Reverse Reaction (Shift Left)**: If the FeSCN²⁺ complex is removed or if Fe³⁺ ions are removed from the solution, the equilibrium will shift to the left to replace the lost FeSCN²⁺. This shift will result in a decrease of the orange color, leading to a **pale yellow** solution as the concentration of Fe³⁺ (which is pale yellow) increases.

3. **Summary of Color Changes**:
- **Adding SCN⁻**: Increased orange (shift to the right).
- **Removing FeSCN²⁺ or Fe³⁺**: Decreased orange leading to pale yellow (shift to the left).

Thus, the observation of a color change from orange to pale yellow indicates a shift towards the formation of reactants (Fe³⁺ and SCN⁻).