Title: CHE2DEV Env Water Qual Quiz 2

Feedback shared by this category's questions, if partly right: 1

Q: Select the correct statement about the extraction of metals using acidic metal chelators
- Diphenylthiocarbazone (dithione) is an acidic metal chelator that forms charged complexes with metals by coordinating through nitrogen and oxygen donor atoms
- The chelated metal ion can be recovered from the organic phase by the addition of a strong base to neutralise the acidic chelator
- At pH < 3, the extraction efficiency of Bi^3+ by diphenylthiocarbazone (dithione) is 100%
- The extraction of Al^3+ by the bidentate chelator 8-hydroxyquinoline (oxine) involves a 3:1 mole ratio of oxine-to-Al^3+
A: The extraction of Al^3+ by the bidentate chelator 8-hydroxyquinoline (oxine) involves a 3:1 mole ratio of oxine-to-Al^3+

Q: Select the correct statement about blank, zero and quality control solutions that are used during the quantitative analysis of sample.
- A zero concentration sample can be prepared by filtering a sample to remove all non-soluble material
- A standard blank is a prepared solution that contains the analyte dissolved in appropriate reagents
- A quality control standard can be prepared from a sample by adjusting its concentration to match that of a standard
- A sample blank is a prepared solution that contains only the reagents in the same amount as that used to ready a sample for analysis
A: A sample blank is a prepared solution that contains only the reagents in the same amount as that used to ready a sample for analysis

Q: Select the correct statement about appropriate sample containers and the storage of environmental water samples.
- Plastic containers are best for samples that are to be analysed for organic herbicide residues by gas chromatography
- On-site addition of a preservative or conditioning reagent is needed for some analyses to prevent sample decomposition
- Samples should be kept at room temperature for long-term storage to prevent precipitation reactions
- Samples to be analysed for heavy metals (such as Pb^2+) by atomic absorption spectrometry are best kept in an inorganic matrix like glass
A: On-site addition of a preservative or conditioning reagent is needed for some analyses to prevent sample decomposition

Q: Select the corrent statement about the quantitative method of multi-point standard addition
- Different volume of sample is added to two volumetric flasks containing incremental volumes of standard
- Incremental volumes of standard are added to a series of volumetric flasks containing the same volume of sample
- Different volumes of sample are added to two volumetric flasks containing incremental volumes of standard
- Incremental volumes of sample are added to a series of volumetric flasks containing the same volume of standard
A: Incremental volumes of standard are added to a series of volumetric flasks containing the same volume of sample

Q: Select the correct statement about the quantitative method of spiking standard addition
- The sample volume change is negligible because of the addition of a small volume of concentrated standard
- One analyte measurement is made following the addition of a small volume of dilute standard to the sample
- Spiking standard addition is a more complex version of single-point standard addition
- Analyte measurements of the sample are made before and after the addition of a large volume of dilute standard
A: The sample volume change is negligible because of the addition of a small volume of concentrated standard

Q: Select the correct statement about the quantitative method of internal standardisation
- A suitable internal standard should have different physical and chemical properties to the analyte
- Variations in sample injection volumes and instrument response characteristics over an extended time period can be minimised when using gas chromatography
- A suitable internal standard should have a different detector response when present at a similar concentration to the analyte
- The response factor indicates the concentration of the internal standard in each sample
A: Variations in sample injection volumes and instrument response characteristics over an extended time period can be minimised when using gas chromatography

Q: Select the correct statement about incremental methods of quantitative analysis.
- Most environmental water and biological samples exist as a complex sample matrix due to the presence of many different inorganic and organic chemical species
- A matrix effect changes the measurement of the analytical signal by a chemical reaction between the analyte and other chemical species in the sample
- Incremental methods are preferred for "simple" samples where the absence of other chemicals does not interfere with detection of the analyte
- Chemical interference results from the presence of other chemicals that mask the analytical signal of the analyte
A: Most environmental water and biological samples exist as a complex sample matrix due to the presence of many different inorganic and organic chemical species

Q: Select the correct statement about sample replicates.
- Poor laboratory technique can be reduced by analysing more sample replicates
- Analysing sample replicates gives the analyst confidence that the measured result is a representative value
- More sample replicates are only required if site conditions will change in the future
- Additional sample replicates are not required if only one type of analysis is to be performed
A: Analysing sample replicates gives the analyst confidence that the measured result is a representative value

Q: Fill in each blank with a single word.
An [...] sampling plan provides [...] samples of the water body. Dividing a site into equal areas and taking a sample from each area is known as [...] sampling. It might be appropriate to use [...] sampling when revisiting a site from which samples have been previously analysed.
A: objective; representative; systematic; judgemental

Q: Fill in each blank with a single word.
Single-point standard addition uses [...] solutions containing the [...] volume of [...] analyte made up to the same [...] volume
A: two; same; unknown; final