Name ___________________________________________ Section ___________ Date ___________________
Experiment # 5
PURIFICATION OF WATER
OBJECTIVE:
To be able to purify water.
MATERIALS:
Watch glass (3)
Distilling flask
Adaptor
Erlenmeyer flask (100mL)
Dropper
River water
Alum solution
Fine soil particles
Iron ring
Condenser
Graduated cylinder
wire gauze
distilled water
phenolphthalein
iron stand (2)
filter paper
iron clamp
funnel
rubber tubings
funnel stand
cork with hole(2) beaker (100mL)
NH4OH (conc.)
NH4OH (dilute)
IMPURITIES OF WATER:
Water may have suspended or dissolved impurities. The dissolved impurities may be volatile or nonvolatile. Water that contains dissolved calcium and magnesium is called hard water. The process of removing
the hardness of water is called water softening. Water that is free from calcium and magnesium salts is called
soft water.
Place the following on three separate watch glasses (WG) and evaporate them to dryness over a water
bath (Fig. 5-a).
WG #1: 1 mL of distilled water
WG #2: 1 mL of river water
WG #3: 1 mL of distilled water to which 1 drop
of
concentrated NH4OH has been added.
Which watch glasses had residue? The residue are the
non-volatile impurities of the water and they may be
dissolved mineral salts and suspended impurities such
dust/soil and bacteria.
as
___________________________________________
Fig 5-a. Apparatus set-up for water bath evaporation
How is an impurity such as ammonia dissolved in water classified?
___________________________________________________________________________________
Name another example of a similar kind of impurity of water.
1
___________________________________________________________________________________
PURIFICATION OF WATER:
a) Elimination of Suspended Solids
Place 10.0 mL of water containing fine soil particles in suspension in a test tube. Add 1.0 mL of
alum solution. Set aside for a few minutes. Compare the water at the upper part with that at the lower
part of the test tube. Filter and compare the filtrate with another 10.0 mL sample of the water that
has not been treated with alum.
____________________________________________________________________________________
What
is
the
role
of
______________________________________________
alum
in
water
purification?
____________________________________________________________________________________
Explain
how
alum
_______________________________________________________________
does
it.
____________________________________________________________________________________
b) Distill 25.0 mL river water, using the set-up shown on Fig.5-b. Collect 5 mL of the distillate. Compare it
with the original water as to smell, taste and clarity.
____________________________________________________________________________________
____________________________________________________________________________________
Add a drop of ammonium hydroxide to the water and continue distilling. Add a drop of
phenolphthalein to the distillate. Is ammonia removed by distillation?
____________________________________________________________________________________
____________________________________________________________________________________
Are volatile impurities removed from the water by distillation? Explain why.
____________________________________________________________________________________
____________________________________________________________________________________
What kind of impurities are removed from the water by simple distillation? How does this experiment
prove your answer?
____________________________________________________________________________________
____________________________________________________________________________________
2
What is distillation? ___________________________________________________________________
____________________________________________________________________________________
Fig. 5-b. Distillation Set-Up
3