a. Using a spatula (spoon) put small amount of I2 in a test-tube.
5cm3 of hydrocarbon solvent and shake.
Colour of the solution: pale violet
c. Add 5cm3 of KI (Without I2).
I2 distributes between 2
solvents: The colour of hydrocarbon-lighter
The colour of the potassium iodate- darker violet.
Hydrocarbon level is on the top and two solvents do not mix. Iodine is soluble in both hydrocarbon and KI.
Conclusion: I2 constantly moves between 2 layers. As the properties of the system (intensity of colour) remain constant, the rate of movement in both direction is the same. Equilibrium state is dynamic.
Proof: if we add radioactive I2 to solution it will distribute itself evenly
using solvents in different order- same
Iodine molecules can move even if the colour change is not noticeable.
a. put 2 samples of I2(aq) in KI into test-tubes.
b. to one add dilute sulphuric acid - does not react
c. to other add dilute NaOH reacts. (colour changes from brown to colourless)
d. Reaction: I2(aq)+Na-(aq)+OH-(aq)IO-(aq))+Na+(aq)+I-(aq)+ H2O
e. If I am going to reverse I am adding acid into my c. to change the pH. Acid reacts with OH- ions (present even in the pure water)
Reaction proved that varying the concentration of OH- can vary the equilibrium.
a. Put 2 samples of Na2CrO4 solutions into test-tubes
b. One sample add dilute acid - reacts, colour from yellow to orange
c. The other add dilute alkali - does not react
d. Repeat 1-3 using Na2Cr2O7 instead. Goes yellow with alkali. Means there are H+ .
a. Put 5cm3 of 0.02M FeCl3 into 3 test-tubes (actually Fe(H2O)63++3Cl-)
b. Put 5cm3 of 0.02M KCNS into each of these tubes goes blood red (Fe(H2O)5(CNS)2+)
c. To one add sodium dihydrogen phosphate until the colour has noticeably changed - requires twice the amount as c.
d. To second add 0.1M sodium ethanedioate - goes easily yellow (little amount)
e. To third add 0.1M NaCl - does not react
Examine saturated KNO3: The bottle of saturated KNO3 contains precipitate or crystals of KNO3 formed at the bottom of the bottle. If it is added to bottle of water, the ions in crystals would become separated by H2O molecules and move apart (precipitate dissolves). KNO3(s) KNO3(aq) is constantly happening.