Question

consider the reaction
fe³⁺(aq) + scn⁻(aq) ⇌ fescn²⁺(aq)
a. how will the equilibrium position shift if
water is added, doubling the volume?
othe reaction will shift to the right
the reaction will shift to the left
b. how will the equilibrium position shift if
agno₃(aq) is added? (agscn is
insoluble.)
othe reaction will shift to the right
the reaction will shift to the left
c. how will the equilibrium position shift if
naoh(aq) is added? fe(oh)₃ is
insoluble.
othe reaction will shift to the right
the reaction will shift to the left
d. how will the equilibrium position shift if
fe(no₃)₃(aq) is added?
othe reaction will shift to the right
the reaction will shift to the left

Explanation:

Step1: Analyze the effect of doubling the volume

When water is added and the volume is doubled, the concentrations of all species \([Fe^{3 + }]\), \([SCN^{-}]\), and \([FeSCN^{2+}]\) are halved.
The reaction quotient \(Q=\frac{[FeSCN^{2 + }]}{[Fe^{3 + }][SCN^{-}]}\). After halving the concentrations, \(Q\) becomes \(\frac{\frac{1}{2}[FeSCN^{2 + }]}{\frac{1}{2}[Fe^{3 + }]\times\frac{1}{2}[SCN^{-}]} = 2\times\frac{[FeSCN^{2 + }]}{[Fe^{3 + }][SCN^{-}]}\), so \(Q > K\) (equilibrium constant).

Step2: Analyze the effect of adding \(AgNO_{3}\)

\(AgNO_{3}\) reacts with \(SCN^{-}\) to form insoluble \(AgSCN\). So \([SCN^{-}]\) decreases.
According to Le - Chatelier's principle, the system will try to increase \([SCN^{-}]\) by shifting the reaction to the left.

Step3: Analyze the effect of adding \(NaOH\)

\(NaOH\) reacts with \(Fe^{3+}\) to form insoluble \(Fe(OH)_{3}\). So \([Fe^{3+}]\) decreases.
According to Le - Chatelier's principle, the system will try to increase \([Fe^{3+}]\) by shifting the reaction to the left.

Step4: Analyze the effect of adding \(Fe(NO_{3})_{3}\)

\(Fe(NO_{3})_{3}\) dissociates to give \(Fe^{3+}\). So \([Fe^{3+}]\) increases.
According to Le - Chatelier's principle, the system will try to decrease \([Fe^{3+}]\) by shifting the reaction to the right.

Answer:

a. The reaction will shift to the left
b. The reaction will shift to the left
c. The reaction will shift to the left
d. The reaction will shift to the right