Analysis of Bottled Water

 

III. Soluble Chloride – Form C

 

Chloride-containing compounds enter surface water, soil, and ground water during snow melt due to the use of road salt, which is an important source of chloride.  Since chloride ions are conservative, they are less likely to degrade into the environment and will remain in solution once dissolved.  When present in large concentrations chlorides can cause a brackish, briny, and salty taste to water.

Sources:

http://wlapwww.gov.bc.ca/wat/wq/BCguidelines/chloride.html

http://www.freedrinkingwater.com/water-education2/76-chloride-sulfate.htm

 

 

AgNO3 (aq) + Cl- (in H2O) → AgCl (s) + NO3- (aq)

 

Procedure:

 

·        Place 20 drops of water sample in a watch glass

·        Add one drop of 1M NaCrO4 indicator

o       Stir with toothpick (The solution should be a pale yellow-green)

·        Titrate with  0.0025M AgNO3 one drop at a time

o       Stir with toothpick after each drop

o       Keep track of the number of drops added

o       Stop at the first appearance of a uniform orange tint

·        Record the number of drops of AgNO3 added

·        Repeat procedure four more times - maintain precision within one drop 

·        Calculate the amount of Chloride in ppm and record data below

·        Transfer all your data to the class data sheet -  Form F

 

Water Samples 

Sample 1:

#1

#2

#3

#4

#5

Average

# of Drops of water

20

20

20

20

20

AgNO3 drops

Drops of AgNO3

 

 

 

 

 

 

 

Sample 2:

#1

#2

#3

#4

#5

Average

# of Drops of water

20

20

20

20

20

AgNO3 drops

Drops of AgNO3

 

 

 

 

 

 

 

Sample 3:

#1

#2

#3

#4

#5

Average

# of Drops of water

20

20

20

20

20

AgNO3 drops

Drops of AgNO3

 

 

 

 

 

 

 

Sample 4:

#1

#2

#3

#4

#5

Average

# of Drops of water

20

20

20

20

20

AgNO3 drops

Drops of AgNO3

 

 

 

 

 

 

 

ppm of Soluble Chloride  = [(0.0025M AgNO3) (Av. drops of AgNO3)(35,500mg/moles)]  ÷ (Av. drops of water samples)

 

                                                       Soluble Chloride Data

Type and Brand of water

Soluble Cl - (ppm)

 

 

 

 

 

 

 

 

 

 

 

 

 

Levels of Soluble Chloride (ppm)

0-250

Acceptable

250-500

Less than desirable

500-1,000

Undesirable

Over 1,000

Unsatisfactory

 

Questions

 

  1. Suppose that during the titration you added sufficient AgNO3 to change the color of the indicator to a darker orange-red. Would this change the results? Explain.
  2. Chlorine is often added to water in small amounts as a disinfectant in drinking water (less than 1 ppm) and swimming pools (approximately 5 ppm). Will this added chlorine have an affect on the chloride level in water?
  3. Based on what you have learned in this experiment, do you consider chloride a serious water pollutant? Why or why not?