Question

can I get some help with question number 8 please

Al equlibrium Q-Keg Extent of reaction 7. Explain the colour change of the (Fe(NO3)3 +KNCS) solution in terms of the equilibrium position in Eq. 10 (see Manual) [1 mark] when excess of Fe(NO3)3 was added > Adding Fello22 changes the colour to a darker red compared to the colour @poulibrium. More products are formed and equilibrium will shift to the right when excess of KNCS was added Adding excess KICS Will Charge the colour to a dark red. Equilibrium will shift to the right more product forms. It is a forwards reaction. 8. How might you lighten the red colour of the (Fe(NO3)3 + KNCS) solution (other than by dilution with a lot of water!)? Explain the basis for your answer. [1 mark]

Answer 1

the complete reaction is given below. (Single headed arrow is actually a biheaded arrow a it is bidirectional reaction.)Colour of product (FeSCN2+) is dark red. While reactant colour is almost colourless.

KSCN + Fe(NO3)3 → FeSCN2+ + KNO3 3

So if we want lighten the colour, we have reduce the amount of product. For this we have to shift the equilibrium to reactant side.

This reaction is an exothermic reaction. So as the reaction proceeds forward heat is released and in backward reaction, heat is consumed.

So if we heat the system externally, temperature will rise. To reduce the temperature, system has to absorb the heat we've given. For this backward reaction has to happen. (As per Lechatelier principle)

So if we heat equilibrium shift to reactant side and more reactant will be there at equilibrium. So the solution lighten(as product concentration is reduced)

So heat to lighten