Question

1) GC can be used for: Group of answer choices

A.Qualitative and Quantitative assessment B.Qualitative assesment C.Quantitative assesment

2) In one of the videos a mixture of methanol and methylbenzene was injected into the GC for separation. Methylbenzene is also known as:Group of answer choices

A.Methylhexene B.Toluene C.Methylhexane

3)The amount of each substance present in the mixture is _____________ proportional to the area under each peak. Group of answer choices

A.inversely B.directly C.not

Answer 1

GC is the abbreviated form of Gas Chromatography. It is an analytical technique used for separation and analysis of compounds that can be vaporized without undergoing decomposition.

PRINCIPLE :

The components of the sample are dissolved in a solvent and then vaporized to separate the analyte by distributing it within two phase: the stationary and the mobile phases. Here, a chemically inert gas serves as the mobile phase which carries the analyte through the heated column and thus carries out the purpose of separation.

1.  Qualitative assessment : The chromatographic data is represented as a graph of detector response against retention time. The time taken for a particular compound to travel through the column to the detector is known as the Retention time (R_t). This time is measured from the time the sample is injected to the point to the time at which the display shows a maximum peak height for that compound. Different compounds have their own characteristic retention times, which enables qualitative analysis. Thus retention time can be used to identify analytes if method conditions are constant.

Quantitative assessment : The area under each peak shown in the detector is proportional to the amount of analyte present in the sample. By using integration, the area under the peak can be calculated, and the concentration of the analyte in the original sample can thus be determined using a calibration curve. This calibration curve can be created by finding the response for a series if concentrations of the same analyte. Thus quantitative assessment is also possible.

So, option (A) is the correct answer.

2. Another chemical name for methylbenzene is toluene.

So, option (B) is the correct answer.

3. From the quantitative assessment part explained in answer 1, it is known that the amount of each substance present in the mixture is directly proportional to the area under each peak.

So, option (B) is the correct answer.