In: Chemistry
What kind of shift occurs when you add KNO3 to the equilibirum reaction: Fe3+ + SCN- <=> FeSCN2
i know the reaction turns into an orange color
Fe3+ ion and SCN- react with each other to form a red complex ion, [FeSCN]2+. If you use very dilute solutions of Fe3+ and SCN- then the color of the product will be faint reddish-orange. In this experiment, if you use much more concentrated solutions , the product solution is a deep red (almost the color of blood).
Fe3+(colorless) + SCN- (colorless) = [FeSCN]2+ (blood red)
In this system, we can tell in which direction the equilibrium shifts when a change is made by monitoring the intensity of color of the system. If the system gets darker red in color, then the equilibrium must be shifting to the right (toward producing more of the colored product). If the color of the system gets fainter (or disappears altogether), the equilibrium must be shifting toward the left (toward the colorless components). You had to be very observant on this part to see the change in intensity of the red color when a drop of reagent was added: if you waited too long, the localized change in color as the droplet enters the equilibrium reaction would fade out.
The additional reagent KNO3 can only change the colour if it can form precipitate in this solution. If we add KNO3 to this solution than Fe(NO3)3 or KSCN can form . But here both Fe(NO3)3 and KSCN are soluble and do not form precipitate . So, according to me there should be not change in intensity of colour. Hence, we can say reaction shifts to left.
But if you are saying that reaction turn into orange color (less intense colour than deep red ) then it means reaction is reactant favoured. So,