a. Using a
spatula (spoon) put small amount of I2 in a test-tube.
b. Add
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
brownish
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.
I2(aq)I2(hydrocarbon)
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
d. Repeat
using solvents in different order- same
result.
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+ .
e. 2CrO42-+2H+Cr2O72-+H2O
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.