M4-Analytical Techniques

Question 1

What happens when IR radiation is passed through a sample

Answer 1

The bonds absorb the IR energy and vibrate more with a stretching or bending motion

Question 2

What type of radiation do bonds absorb

Answer 2

Radiation with the same frequency as the bond in cm-1

Question 3

What are the most abundant greenhouse gases that absorb IR

Answer 3

Carbon dioxide
Water Vapor
Methane

Question 4

What does IR spectroscopy allow us to identify

Answer 4

Functional groups in a molecule

Question 5

How to carry out IR spectroscopy

Answer 5

Place sample in spectrometer
Beam of IR passes through it and the beam that gets through it transmitted and a graph is transmitted on a computer called a spectrum (plural = spectra)

Question 6

What to include when answering IR questions

Answer 6

State the wave number of the peak using data sheet
Write the bond and functional group for the peak
State any peaks that are missing to rule out certain functional groups

Question 7

Applications of infrared spectroscopy

Answer 7

Identification of atmospheric pollutants
To test for drink driving using breathalyser to measure ethanol in the mouth

Question 8

Mass spectrometry use

Answer 8

Identity MR of organic compound
Gain further information about the structure of molecules

Question 9

What happens when molecules are put into a mass spectrometer

Answer 9

Losses an electron forming a positive ion called the molecule ion, M+

Question 10

Most important peaks

Answer 10

The last peak of the spectrum (be careful for M+1 peak) show the MR of the sample
The one with the greatest intensity shows the fragments with the greatest abundance

Question 11

Why do M+1 peaks exist

Answer 11

As 1.1% do carbon exists as a C13 isotope

Question 12

Hoe to write fragments out

Answer 12

Square brackets with + charge. When a sample is broken, only one of the 2 products are a positive fragment