OCR A-Level Chemistry Synthesis and analytical techniques (02), November 2020: Question 13

1 mark · Medium difficulty · Multiple Choice

Identify the correct statements regarding gas chromatography involving retention times, peak areas, and calibration curves

Practise this question

Question

Multiple-choice question 13 asking which statements about gas chromatography are correct among three numbered statements: 1, components can be identified from retention time; 2, relative peak areas give proportions; 3, calibration curves confirm concentrations. Four options A, B, C, D are listed below with an answer box.
Question text

13 Which statement(s) is/are correct for gas chromatography?

1 The components in a mixture can be identified from their retention time.

2 The relative peak areas give the proportions of components in a mixture.

3 Calibration curves are used to confirm the concentrations of components in a mixture.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer

[1]

Mark scheme

Show the mark scheme Mark scheme showing the correct answer for question 13 is option A.

13 A 1 1.1

How to answer it

Gas Chromatography Analysis

What this question tests

This question assesses your understanding of analytical techniques—specifically Gas Chromatography (GC). It evaluates your knowledge of how retention times are used for qualitative identification, how peak areas correlate to component proportions, and how calibration curves allow quantitative determination of concentration in a mixture.

Question 13

Analyzing Statements on Gas Chromatography

✅ Correct Answer: A (1, 2 and 3)

All three statements regarding the principles and applications of gas chromatography are completely accurate.

💡 Key Knowledge

  • Statement 1: Retention time is characteristic of a specific compound under fixed conditions, allowing qualitative identification.
  • Statement 2: The area under each chromatographic peak is directly proportional to the relative amount/proportion of that component in the mixture.
  • Statement 3: Calibration curves (plotting peak area versus known concentration) are standard practice to accurately determine unknown concentrations.

🧠 Exam Technique

When faced with roman numeral statements in multiple-choice questions, evaluate each statement independently. If you confirm statements 1 and 3 are correct, you can immediately rule out options B and D, narrowing your focus quickly.

❌ Common Errors

Students often mistakenly believe that peak height is used to determine proportions or concentrations. Always remember that peak area is the correct quantitative measure, as peak shapes can broaden.

Mark Scheme Allocation: 1 mark awarded for selecting A.

Topics

Module 6: Organic chemistry and analysis · 6.3 Analysis

Question and mark scheme from the OCR A-Level Chemistry examination, Synthesis and analytical techniques (02), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.