Spectroscopy

Question 1

greenhouse gases.(They trap the Earth’s radiated infra red energy
in the atmosphere).

Answer 1

Carbon dioxide (CO2), methane (CH4) and the main one
water vapour (H2O)

Question 2

IR abosrptions of the C=O, O–H and C–H bonds in H2O, CO2

and CH4 contribute to what?

Answer 2

global warming

Question 3

what does The ‘Greenhouse Effect’ of a given gas depend on

Answer 3

is
dependent both on its atmospheric concentration
and its ability to absorb infrared radiation and
also its residence time. (Time it stays in
atmosphere)

Question 4

uses of IR

Answer 4

Modern breathalysers measure ethanol in the breath by analysis using infrared spectroscopy
Infrared spectroscopy can be used to monitor gases causing air pollution (e.g. CO and NO from car
emissions)

Question 5

describe whats happening

Answer 5

Molecular ion formed: M → [M]+. + e–
The molecule loses an electron and
becomes both an ion and a free radical

Question 6

why does the The Molecular ion fragments

Answer 6

The Molecular ion fragments due to covalent bonds breaking: [M]+. → X+ + Y.

Question 7

what strength of peak intensity does a stable ion have

Answer 7

great

Question 8

what uses the same tech as NMR spectroscopy

Answer 8

‘magnetic resonance

imaging’ (MRI) to obtain diagnostic information about internal structures in body scanners

Question 9

why are Samples are dissolved in solvents without any 1H atoms, e.g. CCl4, CDCl3

Answer 9

This means that in the H NMR the

solvent will not give any peaks

Question 10

why add TMS

Answer 10

A small amount of TMS (tetramethylsilane) is added
to the sample to calibrate the spectrum
TMS is used because:
•its signal is away from all the others
•it only gives one signal
•it is non-toxic
•it is inert
•it has a low boiling point and so can be removed
from sample easily

Question 11

what happens what d2o added

Answer 11

If D2O is added to a sample then a process of proton

exchange happens with the H in any O-H and N-H bonds.