In the video, the host demonstrates Le Chatelier's principle by adding sodium phosphate to a solution of iron thiocyanate. What is the observed effect of this addition on the equilibrium of the reaction?

Question

A. The solution turns darker red, indicating an increase in the concentration of iron thiocyanate.
B. The addition of sodium phosphate has no observable effect on the equilibrium of the reaction.
C. The solution becomes cloudy, indicating the formation of a precipitate.
D. The solution becomes colorless, indicating a shift towards the reactants, iron and thiocyanate ions.

Answer 1

The observed effect of adding sodium phosphate to a solution of iron thiocyanate can be analyzed through Le Chatelier's principle. In this case, sodium phosphate can react with iron ions to form a precipitate of iron phosphate, thereby reducing the concentration of available iron ions in the solution.

When the concentration of one of the reactants (in this case, iron ions) decreases, according to Le Chatelier's principle, the equilibrium will shift in the direction that produces more of those reactants to counteract the change. Therefore, the reaction will shift to the left, favoring the formation of the reactants and reducing the concentration of iron thiocyanate.

Thus, the correct answer is:

D. The solution becomes colorless, indicating a shift towards the reactants, iron and thiocyanate ions.