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Explain how the classical methods of analytical chemistry can be used to determine information about alcohols - VCE - SSCE Chemistry - Question 10 - 2020 - Paper 1
Question 10
Explain how the classical methods of analytical chemistry can be used to determine information about alcohols. In your answer, refer to: - qualitative analysis and ... show full transcript
Worked Solution & Example Answer:Explain how the classical methods of analytical chemistry can be used to determine information about alcohols - VCE - SSCE Chemistry - Question 10 - 2020 - Paper 1
Step 1
Qualitative analysis and how it can be used to determine whether a compound is an alcohol and, if it is, the type of alcohol
Answer
Qualitative analysis involves identifying the chemical composition and functional groups present in a compound. For alcohols, specific tests can indicate the presence of the hydroxyl group (-OH).
One common method is to react the compound with a reagent like potassium dichromate (Cr2O7^2- in acid), which will oxidize primary and secondary alcohols, producing a color change. If no color change occurs, it may indicate the presence of a tertiary alcohol or the absence of an -OH group. Additionally, a simple smell test can help identify alcohols; they often have distinct odors.
To determine the type of alcohol, further tests can be conducted, like reacting the alcohol with bromine (Br2), which can reveal whether it's primary, secondary, or tertiary based on the reaction outcome.
Step 2
Quantitative analysis
Answer
Quantitative analysis involves measuring the amount of a substance in a mixture or solution. For alcohols, this can often be performed using titration methods.
For example, a redox titration can be used, where the alcohol is oxidized by a reagent like potassium permanganate (KMnO4) in an acidic medium. The endpoint can be determined through a color change, allowing for the calculation of the volume of alcohol present.
The concentration can also be determined by measuring the absorbance using techniques like spectroscopy, correlating the absorbance to the concentration using Beer's Law.