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Explain TWO errors that this scientist is making while collecting the blood sample - HSC - SSCE Chemistry - Question 36 - 2060 - Paper 1
Question 36
Explain TWO errors that this scientist is making while collecting the blood sample. Hydrolysis can be used to break down proteins into amino acids. This equation r... show full transcript
Worked Solution & Example Answer:Explain TWO errors that this scientist is making while collecting the blood sample - HSC - SSCE Chemistry - Question 36 - 2060 - Paper 1
Step 1
Explain TWO errors that this scientist is making while collecting the blood sample.
Answer
The forensic scientist is not wearing gloves and has uncovered hair.
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Contamination Risk: Not wearing gloves can transfer personal contaminants to the blood sample, potentially compromising the integrity of the evidence.
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Hair Exposure: Having uncovered hair could lead to hair falling into the sample, which could also affect the sample's credibility.
Step 2
Step 3
Describe how protein hydrolysis is used in forensic analysis.
Answer
Protein hydrolysis is utilized in forensic analysis to break down complex proteins into their constituent amino acids. This process allows forensic scientists to identify and quantify proteins in a sample, which can be critical for determining the presence of specific bodily fluids. Techniques like electrophoresis can help separate the amino acids, facilitating further analysis of the sample's origin.
Step 4
Using the information in the table, identify the unknown substance and justify your choice.
Answer
The unknown substance is Cocaine. This conclusion is based on the mass spectrum which shows fragments at 82, 94, and 182 mass to charge ratios, matching the significant fragments listed for cocaine in the table provided.
Step 5
Describe how mass spectrometry can be useful for analysing forensic evidence.
Answer
Mass spectrometry is highly effective in analyzing forensic evidence due to its ability to provide precise molecular weight measurements and structural information about compounds. It can differentiate between substances based on their mass-to-charge ratios and can be coupled with chromatography techniques for enhanced analysis. This allows for the identification of compounds even in complex mixtures, improving the reliability of forensic analysis.
Step 6
Outline a valid procedure that could be used in a school laboratory to carry out the investigation.
Answer
To separate organic compounds using chromatography in a school laboratory, follow these steps:
- Take a handful of organic sample and grind it in a mortar with about 10mL of acetone.
- Use filter paper and place it in a capillary tube up to a mark at 2 cm from the bottom.
- Place the tube in a measuring cylinder that contains a suitable solvent such as ethanol.
- Allow the solvent to travel up the filter paper as it absorbs, separating the pigments in the sample based on solubility.
Step 7
Describe TWO limitations of carrying out the procedure outlined in part (i).
Answer
- Limitations on Solvents: The choice of solvent can significantly affect the resolution of the separation. Non-polar solvents may not separate polar components effectively, leading to incomplete analysis.
- Resolution of Separation: The experiment may not provide adequate resolution, meaning different compounds might not separate properly on the filter paper, making qualitative analysis challenging.
Step 8
Explain why DNA evidence may be challenged when used in court cases.
Answer
DNA evidence can be challenged in court due to potential contamination issues during collection or handling, leading to unreliable results. Additionally, the procedures involved in DNA analysis may not be uniformly standardized, which could introduce variability in results. Lastly, the interpretation of DNA evidence can vary, especially if multiple individuals' DNA profiles are present, rendering conclusive matching difficult. Such factors can affect the credibility and weight of DNA evidence in legal proceedings.