Explain what is observed when
( i) Silver nitrate solution is added to potassium ioiodide solution
(ii) The size of the finest gold Sol particles increases in ththe gold solsol
(iii) Two oppositely charged sols areare mixed in a almost equal proportions
(i) When silver nitrate is added to a slight excess of dilute solution of potassium iodide, a negatively charged sol of silver iodide is formed . It is due to the adsorption of iodide ions (I-) from the dispersion medium on the precipitate of silver iodide (AgI).
AgNO3 + KI → AgI + KNO3
AgI + I− → [AgI]I- (negatively charged AgI sol)
a) Tiny particles of gold (one hundred nanometers in diameter) are called gold nano particles, which are very useful. These gold nano particles produce vibrant colours. When these gold nano particles are suspended in solution, solution appears red and as particle size increases solution turns pale blue, purple and colourless. These colours depend on size, concentration of gold nano particles in solution.
AgNO3 + KI → AgI + KNO3
AgI + I− → [AgI]I- (negatively charged AgI sol)
a) Tiny particles of gold (one hundred nanometers in diameter) are called gold nano particles, which are very useful. These gold nano particles produce vibrant colours. When these gold nano particles are suspended in solution, solution appears red and as particle size increases solution turns pale blue, purple and colourless. These colours depend on size, concentration of gold nano particles in solution.
The vibrant colours show gold nano particles interaction with light. These nano particles are efficient in absorbing specific frequencies and intensely scattering other frequencies. This property depends on size, shape, environment of gold nano particles. Hence individual gold paricles is red as it scatters red light more intensely but when many of nano particles mixed together then it appears blue or purple as it scatters blue or purple light more intensely. As gold nano particles do not scatter frequencies of other colours they will not appear in other colours.
b) Mutual precipitation- When two oppositely charged sols are mixed in equimolar proportions, they mutually neutralise their charge and both get coagulated.