CHEMISTRY FOR STPM SCHOOL-BASED ASSESSMENT :

PRACTICAL CHEMISTRY

EXPERIMENT 1: Equilibrium and solubility

The following result and answers are used as guidelines for calculation and solution for the question of (c) to (g)

V0 = volume of Pb(NO3)2
V = volume of KI

Note: Kxp is not affected by the change of concentration used in each experiment.

Try to get almost constant reading from KA1 to KA4.

(e) The values of the ionic product of PbI2 are almost constant for all the experiments.
(f) Average reading = (c1 + c2 + c3 + c4) / 4
(g) Increasing the concentration of lead (II) ions do not affect the value of Ksp of PbI2.

CHEMISTRY FOR STPM

SCHOOL-BASED ASSESSMENT : PRACTICAL CHEMISTRY

EXPERIMENT 10: Ionic Equilibrium

The following result and answers are used as guidelines for calculation and solution for the question of (c) to (g)

Results:
(b) Record and complete your readings in the table below:









(d) Dilution decreases the concentration and hence increases the pH
(e) Dilution decreases the concentration and hence increases the degree of dissociation
(f) as shown in the table above.
(g) Dilution has no effect on Ka.

Precaution step:
the bulb of pH meter must be immersed in the buffer solution before next measurement is being carried out.
measurement of pH should can done from the most diluted acid to the most concentrated acid in order to attain more accurate reading of pH.