Experiment 11.1 p.290.

1.

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.

I_2(aq)I_{2(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.

2.

a.     put 2 samples of I_2(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: I_2(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.

3.

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.    2CrO₄^2-+2H⁺Cr₂O₇^2-+H₂O

4.

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

5.

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). KNO_3(s) KNO_3(aq) is constantly happening.