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The above diagram shows the gas chromatogram of a sample containing four straight chain alkanes - VCE - SSCE Chemistry - Question 6 - 2009 - Paper 1
Question 6
The above diagram shows the gas chromatogram of a sample containing four straight chain alkanes. The following statements refer to this chromatogram. I The boiling... show full transcript
Worked Solution & Example Answer:The above diagram shows the gas chromatogram of a sample containing four straight chain alkanes - VCE - SSCE Chemistry - Question 6 - 2009 - Paper 1
Step 1
I The boiling points of the compounds arranged from highest to lowest are Z > Y > X > W.
Answer
This statement is true. The boiling points of straight chain alkanes increase with the number of carbon atoms. Since the order given is Z (150) > Y (75) > X (100) > W (200) based on their peak area responses, it indicates that Z has the highest boiling point followed by Y, then X, and W has the lowest.
Step 2
II The retention times will stay the same if the temperature at which the chromatogram is recorded is increased, all other conditions remaining constant.
Answer
This statement is false. Increasing temperature generally decreases the retention time of compounds in gas chromatography. Higher temperatures reduce the interaction between the analytes and the stationary phase, allowing them to elute faster.
Step 3
III Hydrogen gas could have been used as a carrier gas to obtain this chromatogram.
Answer
This statement is true. Hydrogen gas is often used as a carrier gas in gas chromatography due to its excellent efficiency in carrying analytes through the column, providing improved resolution and reduced analysis time.