Question

The retention time for cyclohexane on a gas chromatography instrument is 0.75 minutes. The temperature of the gas chromatography column is 70 degrees C and the gas flow rate is 60 mL/minute.

(a) Would the retention time be higher or lower if the column temperature is raised to 100 degrees C?
(b) Would the retention time be higher or lower if the flow rate is changed to 30 mL/minute?
(c) Would the retention time be higher or lower if the column length was decreased to 1/2 the length?

Answer 1

(a) Lower

(b) Higher

(c) Higher

Step-by-step explanation:

Gas chromatography is a common type of chromatography used in chemistry for separating and analyzing compounds that can be vaporized without decomposition. The interaction of chemicals with the stationary phase cause different retention times in different compounds.

(a) Would the retention time be higher or lower if the column temperature is raised to 100 degrees C? The raising of column temperature will produce an increasing in vaporization of cyclohexane doing retention time lower.

(b) Would the retention time be higher or lower if the flow rate is changed to 30 mL/minute? A decreasing in the flow rate will produce the rate of the cyclohexane decrease doing retention time higher.

(c) Would the retention time be higher or lower if the column length was decreased to 1/2 the length? If column lenght was decreased the cyclohexane must travel less distance doing retention time higher.

I hope it helps!