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This question is about methods of analysis - AQA - GCSE Chemistry - Question 5 - 2017 - Paper 1
Question 5
This question is about methods of analysis. A student wanted to compare the colours in two inks, A and B, using paper chromatography. 5 (a) (i) Describe a method t... show full transcript
Worked Solution & Example Answer:This question is about methods of analysis - AQA - GCSE Chemistry - Question 5 - 2017 - Paper 1
Step 1
Describe a method the student could use.
Answer
To compare the colours in inks A and B using paper chromatography, the student should follow these steps:
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Preparation of the paper: Draw a horizontal baseline using a pencil about 2 cm from the bottom of the chromatography paper.
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Application of inks: Place small dots of each ink (ink A and ink B) directly on the baseline, ensuring they do not touch each other.
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Placement in solvent: Carefully immerse the bottom of the paper into a suitable solvent (e.g., water), ensuring the solvent level is below the baseline.
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Development of chromatogram: Allow the solvent to rise up the paper by capillary action, carrying the different ink components with it.
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Finishing the process: Once the solvent has traveled a sufficient distance, remove the paper and let it dry. Lines of different colours will appear, indicating the separation of the ink components.
Step 2
Compare the colours in the inks A and B.
Answer
Upon analyzing the results in Figure 6:
- Ink A has three distinct colours, while Ink B has four.
- It is observed that two colours from both inks are identical, signifying a similarity in their composition.
- However, there is one colour present in Ink A that is absent in Ink B, and conversely, Ink B contains two additional colours not found in Ink A.
This indicates that while both inks share some commonalities in their colour components, they also exhibit distinct differences.
Step 3
Describe how gas chromatography separates substances in a mixture of compounds.
Answer
Gas chromatography (GC) operates on the principle of separating volatile substances carried by a gas. The process involves the following steps:
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Sample Introduction: The mixture of compounds is vaporized and introduced into the chromatography column, which is often packed with a stationary phase material.
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Separation Mechanism: As the gas (mobile phase) carries the vaporized sample through the column, different substances interact with the stationary phase to varying degrees. Those that interact less will move faster, while those that have stronger interactions will move slower.
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Detection of Compounds: This differential movement results in substances emerging from the column at different times, allowing effective separation based on their respective retention times.
Step 4
What information about each substance is given by the mass spectrometer?
Answer
The mass spectrometer provides crucial information about each substance such as:
- Relative molecular mass: This indicates the mass of the molecules present in the sample, which can help in identifying the compounds based on their mass-to-charge ratio (m/z).
- Structural information: It can provide insights into the molecular structure and fragmentation patterns of the substance, aiding in identification.