Laboratory Report Sheetexperiment

Part A. Measurement of the dissolved oxygen level (D.O.) of an air-saturated sample of D.I. water and a direct sample of tap water

Experimental data

Sample A#l: Air-saturated D.I. water

Temperature:_

Barometric pressure:_

Sample volume used:_

Color of the observed precipitate after the first two reactant additions:_

Sample A#2: Tap water

Temperature:_

Barometric pressure:_

Sample volume used:_

Color of the observed precipitate after the first two reactant additions:_

Titrant:_Titrant concentration:_

Sample

mL of titrant

D.O. concentration, mg/L

Air-saturated D.I. water

Tap water

Part B. Dissolved oxygen measurement of an aerated D.I. sample treated with a reducing agent

Experimental data

Sample B#l: Aerated D.I. sample treated with a reducing agent

Temperature:_

Barometric pressure:_

Sample volume used:_

Reducing agent:_

Color of the observed precipitate after the first two reactant additions:_

Titrant:_Titrant concentration:_

Sample

mL of titrant

D.O. concentration, mg/L

B#1

How does the value compare with the two previous samples? Was the reducing agent efficient?

Part C. Effect of temperature in the dissolved oxygen level in water

Barometric pressure:_

Sample volume used:_

Titrant:_Titrant concentration:_

Sample

D.O. concentration,

Sample

temperature, °C

mL of titrant

mg/L

A#1

C.a

C.b

C.c

How do the values vary with temperature?

Part D. Effect of ionic strength (or salt content) in the dissolved oxygen level in water Experimental data

Barometric pressure:_

Sample volume used:_

Titrant:_Titrant concentration:_

Theoretical

Cone. NaCl,

ionic strength,

D.O. concentration,

Sample

mg/L

I(moUL)

mL of titrant

mg/L

Ml

0

0

D.a

D.b

D.c

Formula used and calculations for the ionic strength:

Formula used and calculations for the ionic strength:

Draw a graph ofD.O. concentration as a function of ionic strength.

Part E. Dissolved oxygen measurement of two samples of river or lake surface water: 1) Fixing the oxygen on site, and 2) after transporting it to the laboratory.

Experimental data

Sample E#l: Surface water measured on site Source:_

Description of site and place (level) of sampling:_

Sampling conditions or precautions:_

Temperature:_

Barometric pressure:_

Sample volume used:_

Color of the observed precipitate after the first two reactant additions:.

Sample E#2: Surface water measured at the laboratory

Source:_

Description of site and place (level) of sampling:_

Sampling conditions or precautions:.

Temperature:_

Barometric pressure:_

Sample volume used:_

Color of the observed precipitate after the first two reactant additions:. Titrant:_Titrant concentration:_

% saturation with

D.O. concentration,

respect to saturated

Sample

mL of titrant

mg/L

D.I. water

E#1

E#2

POSTLABORATORY PROBLEMS AND QUESTIONS

1. Does the value of the measured parameter differ from one sample to another? What may be the causes of such differences?

2. Explain how you calculated the saturation percentage of the samples.

3. Is each D.O. level acceptable for aquatic life? Why?

4. Why is it important to measure this parameter on site?

Student Comments and Suggestions

Literature References

Ondrus, M. G. Laboratory Experiments in Environmental Chemistry, Wuerz Publishing: Winnipeg, Canada, 1993.

Sawyer, C. N.; McCarty, P. L.; Parkin, G. F. Chemistry for Environmental Engineering, 5th ed.; McGraw Hill: New York, 2003.

Stumm, W.; Morgan, J. J., Aquatic Chemistry: Chemical Equilibria and Rates in Natural Waters', Wiley Interscience: New York, 1996.

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