Apentix/AP Chemistry/Unit 7: Equilibrium/Question

AP Chemistryeasymcq1 pt

A solution sits at equilibrium: Fe³⁺(aq) + SCN⁻(aq) ⇌ FeSCN²⁺(aq). What happens when extra Fe³⁺(aq) is added?

A.Nothing changes because Fe³⁺ is already a reactant

B.The equilibrium shifts right, forming additional FeSCN²⁺

C.The equilibrium shifts left, decomposing FeSCN²⁺

D.The value of K increases

Explanation

Core Concept

Adding Fe³⁺ makes the ion product momentarily exceed K, so Q rises above K right after the addition. The system consumes the excess reactant by running the forward reaction until Q falls back to K. Extra FeSCN²⁺ forms and the blood-red color deepens, a classic demonstration of concentration stress. K itself never moves because temperature is unchanged.

Correct Answer

BThe equilibrium shifts right, forming additional FeSCN²⁺

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