1. The Fe3+-ion and salicylic acid (SA) react to give a complex. The equilibrium reaction is Fe3+ + SA ⇌ FeSA3+. A volume of 20 mL of a Fe3+-solution is added to 30 mL of a salicyl... 1. The Fe3+-ion and salicylic acid (SA) react to give a complex. The equilibrium reaction is Fe3+ + SA ⇌ FeSA3+. A volume of 20 mL of a Fe3+-solution is added to 30 mL of a salicylic acid solution. Both solutions have a concentration of 5.00 × 10-4 mol L-1. At equilibrium the complex concentration ([FeSA3+]) is 1.56 × 10-4 mol L-1. Calculate the equilibrium constant (K) for the formation of the complex FeSA3+. 2. When the aforementioned solution at equilibrium is diluted 4 times it appears that [FeSA3+] is less than 1/4 × 1.56 × 10-4 mol L-1. Give an explanation for this. If you have trouble finding the answer, ask yourself if the ratio of concentrations equals K just after dilution. 3. In this practical course a stock solution of Fe3+ is available. Assume that its concentration of is 8.25 × 10-4 mol L-1 Fe3+. Suppose you have to prepare 1 L of such a solution. How much (in g or mg) of the salt FeNH4(SO4)2 · 12 H2O is needed to prepare 1 L?
Understand the Problem
The image contains three chemistry questions. The first question requires the calculation of the equilibrium constant (K) for the formation of a complex ion. The second question requires an explanation for why the concentration of the complex ion decreases upon dilution. The third question involves calculating the mass of a salt needed to prepare a solution of a specific concentration.
Answer
1. K = 2.17 2. Le Chatelier's principle. 3. 0.404 g
- K = 2.17
- The system shifts to the left to re-establish equilibrium, according to Le Chatelier's principle.
- 0.404 g of FeNH4(SO4)2 · 12 H2O is needed to prepare 1 L
Answer for screen readers
- K = 2.17
- The system shifts to the left to re-establish equilibrium, according to Le Chatelier's principle.
- 0.404 g of FeNH4(SO4)2 · 12 H2O is needed to prepare 1 L
More Information
Le Chatelier's principle states that changes in concentration, temperature, volume, or pressure to a system in equilibrium will result in a predictable and opposing shift in the equilibrium.
Tips
Pay attention to units and significant figures in equilibrium calculations to avoid mistakes.
Sources
- Le Chatelier Lab ANSWERS: Fe3+ and FeSCN2+ Equilibrium - youtube.com
- 4.4 – Le Châtelier's Principle - eCampusOntario Pressbooks - ecampusontario.pressbooks.pub
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