For each lake: Based on information from all stages, indicate what chemicals or
ID: 911174 • Letter: F
Question
For each lake: Based on information from all stages, indicate what chemicals or contaminants may be present. Explain your inferences and if your performed any calculations or consulted any databases include these in your results (calculations don’t need to be typed, but they should include units). Evaluate the evidence you are using, the level of confidence for each result and outline precautions and clean-up solutions for every lake.
Lake
pH Test
Residue after Water Evaporation from 1 mL sample
Combustion or other analysis results
Other observations
A
6.5
0.2 g of white solid
No combustion results.
Na 14.3%, H 6.2%, O 69.5%, S 10.0%
Solid is very soluble to water. Upon heating the original white residue loses 56% of its mass as water and appears as white crystalline solid.
B
6.0
0.002 white solid
No combustion results
Largest lake. Small fish still was swimming.
C
NA
NA
NA
Fumes observed. Very small pond with charred wood around it. Severe irritation to the eyes, respiratory tract and mucous membranes prohibited further testing
D
3.2
NA
NA
Adjacent to lake C. Metal thermometer probe registered high temperature but quickly dissolved and produced bubbles of colorless gas.
E
6.5
Small amounts of white and brown solids
NA
Liquid sample displayed 2 immiscible layers. Upon addition of blue CuSO4 powder the top layer becomes blue.
F
8.5
White solid from the aqueous layer
Top layer was combusted and was 83.7% C, 16.3% H.
The top layer was analyzed by Mass Spectrometry and found to have a molecular mass of 86 amu.
Liquid sampled displayed 2 immiscible layers. Upon the addition of blue CuSO4 powder the bottom layer becomes blue. The white solid that was dissolved in the bottom layer had a melting point of 310oC.
G
6.0
White solid
No combustion results
Upon heating the white solid disappears without melting.
Lake
pH Test
Residue after Water Evaporation from 1 mL sample
Combustion or other analysis results
Other observations
A
6.5
0.2 g of white solid
No combustion results.
Na 14.3%, H 6.2%, O 69.5%, S 10.0%
Solid is very soluble to water. Upon heating the original white residue loses 56% of its mass as water and appears as white crystalline solid.
B
6.0
0.002 white solid
No combustion results
Largest lake. Small fish still was swimming.
C
NA
NA
NA
Fumes observed. Very small pond with charred wood around it. Severe irritation to the eyes, respiratory tract and mucous membranes prohibited further testing
D
3.2
NA
NA
Adjacent to lake C. Metal thermometer probe registered high temperature but quickly dissolved and produced bubbles of colorless gas.
E
6.5
Small amounts of white and brown solids
NA
Liquid sample displayed 2 immiscible layers. Upon addition of blue CuSO4 powder the top layer becomes blue.
F
8.5
White solid from the aqueous layer
Top layer was combusted and was 83.7% C, 16.3% H.
The top layer was analyzed by Mass Spectrometry and found to have a molecular mass of 86 amu.
Liquid sampled displayed 2 immiscible layers. Upon the addition of blue CuSO4 powder the bottom layer becomes blue. The white solid that was dissolved in the bottom layer had a melting point of 310oC.
G
6.0
White solid
No combustion results
Upon heating the white solid disappears without melting.
Explanation / Answer
A) Na2SO4.10H20 the only soluble salts of sulphur and sodium are sulphates. Since it loses water it have to be a hydratated salt.
B) it could be a nitrate salt. nitrates forms when low oxygen is present because ammonia consumes oxygen from the water and bacteria transforms it in nitrite and nitrates.
C) SO2 . It oxydizes in air to SO3 that is irritant to the eyes, pulmons, mucous membranes. When SO3 enters in contact with water forms H2SO4 that carbonizes organic matter.
D) H2SO4 lake. Acid dissolves metals
E) WAter (showed by CuSO4) and a kind of oil more dense that water. The other layer could be an halogenated hydrocarbon because they are colorless liquids denser than water. .
F) The %C and % H brings to hexane. C6H14. This also have a molar weight of 86 uma. The water is slightly basic so you can think on NaOH that have a melting point of 318 oC (wikipedia)
G) naphtalene it is a white solid known by sublimating.
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