Title: CHE2DEV Env Water Qual Topic 1

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Q: Select the correct statement about the method of Biochemical Oxygen Demand (BOD) for the analysis of an environmental water sample.
- A BOD_5 value involves the difference in the dissolved oxygen content of a sample measured initially and then after 5 hours
- Measurement of BOD involves addition of oxidising chemicals like dichromate, Cr_2O_7^2-, to kill microorganisms
- The oxygen consumption by microorganisms during the metabolism of biodegradable organics is indicated by a BOD value
- Additional nutrients and microorganisms need to be added for a total BOD value for all organics
A: The oxygen consumption by microorganisms during the metabolism of biodegradable organics is indicated by a BOD value

Q: The Winkler Method for the determination of the dissolved oxygen content of a water sample involves:
- direct titrimetric method involving a series of non-redox reactions
- addition of MnO_2 to liberate dissolved oxygen
- acidification to liberate iodide that is subsequently reduced by oxygen
- addition of Mn^2+ and alkaline iodide to "fix" dissolved oxygen as MnO_2
A: addition of Mn^2+ and alkaline iodide to "fix" dissolved oxygen as MnO_2

Q: Determination of the dissolved oxygen content of a water sample using the Clarke Electrode involves:
- a hydrophilic oxygen impermeable membrane
- a potentiometric measurement of the voltage generated
- oxidation of hydroxide at the anode
- reduction of oxygen at the cathode
A: reduction of oxygen at the cathode

Q: Select the correct statement about the Dissolved Oxygen (DO) content of an environmental water sample.
- increasing the characteristic solubility of oxygen will result in a higher DO content
- an increase in water salinity will lower the DO content
- the DO content will be greater under stagnant compared to dynamic conditions
- a DO content of 4 mg/L indicates a healthy aquatic ecosystem
A: an increase in water salinity will lower the DO content

Q: Select the correct statement about the measured oxidation reduction potential (ORP) of a water sample as determined with a Pt indicator and Ag/AgCl reference electrode.
- ORP is a direct measure of the dissolved oxygen content
- ORP is a measure of the total amount of inorganic and organic species
- "Healthy" surface water is indicated by a ORP value of 515 mV (pH 7, 25^oC).
- The presence of excess oxidising species is indicated by a ORP value of 198 mV (pH 7, 25^oC)
A: "Healthy" surface water is indicated by a ORP value of 515 mV (pH 7, 25^oC).

Q: A low level of water hardness of a water sample is considered beneficial because:
- buffering action of dissolved salts increases the effect of acidic pollutants
- resulting alkalinity lowers the solubility of some toxic metals
- buffering action of dissolved salts decreases the effect of basic pollutants
- resulting acidity lowers the solubility of some toxic metals
A: resulting alkalinity lowers the solubility of some toxic metals

Q: Select the correct statement about the method of Total Organic Carbon (TOC) for the analysis of an environmental water sample.
- TOC measurements are not as reproducible as BOD or COD
- TOC method involves oxidation of carbon in organics to CO_2 by combustion or wet oxidation
- Ion chromatography can be used to directly measure the CO_2 produced
- TOC is the most reliable method to determine oxygen demand
A: TOC method involves oxidation of carbon in organics to CO_2 by combustion or wet oxidation

Q: Select the correct statement about the method of Chemical Oxygen Demand (COD) for the analysis of an environmental water sample.
- The COD method involves an aggressive chemical oxidation of organic matter using strong acid and dichromate, Cr_2O_7^2-
- Silver ions, Ag^+, are added to slow the oxidation of linear hydrocarbon alcohols
- Values for COD are typically half that of BOD for the same samples
- Volatile organics are removed by bubbling hydrogen sulfide, H_2S, through the sample before analysis
A: The COD method involves an aggressive chemical oxidation of organic matter using strong acid and dichromate, Cr_2O_7^2-

Q: Some indicators that can be used to assess water quality are:
- natural indicators like shellfish that can be analysed for toxic metals in their shells and toxic organics in their soft tissues
- a chemical measure like turbidity that involves direct measurement of the transmitted light through a sample (stormwater discharge is not a natural environmental factor)
- a physical measure like water hardness that involves a EDTA titration at pH 7 for the Ca^2+ and Mg^2+ content
- a chemical measure like conductivity that indicates the total dissolved solids in a sample
A: natural indicators like shellfish that can be analysed for toxic metals in their shells and toxic organics in their soft tissues

Q: Physical properties of a water sample that are routinely used to monitor water quality are:
- colour, turbidity, conductivity and dissolved oxygen
- odour, transparency, pH and total phosphate
- taste, turbidity, dissolved oxygen and water hardness
- odour, turbidity, temperature and total dissolved solids
A: odour, turbidity, temperature and total dissolved solids

Q: Source of bromine in this experiment is:____________________
A: NaBr

Q: Sodium Hypochlorite is an _________________agent
A: oxidising