Unit 4Spectroscopy and chromatography Flashcards Preview

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Flashcards in Unit 4Spectroscopy and chromatography Deck (18)
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1
Q

What are the different types of analysis?

A

Infrared, microwaves, ultra-violet and radio waves.

2
Q

How does infrared analysis work?

A

infra red energy causes bonds to vibrate. This can be used to identify the types
of bond in a molecule

3
Q

How does microwave analysis work?

A
  • certain molecules absorb the microwaves causing them to rotate
4
Q

How does radio waves and NMR analysis work?

A

It causes the hydrogen nucleus to change its spin state. This can give us
information about the arrangements of hydrogens in a molecule.

5
Q

How can UV light get used in analysis?

A

UV energy can break bonds such as the Cl-Cl bond or C-Cl

bond

6
Q

When NMR is used, what are the substances dissolved in?

A

Ones without any H atoms like CCl4

CDCl3

7
Q

Why is tetramethylsilane added to NMR?

A
It is used to calibrate the spectrum so you know by how much the peaks have shifted by.
TMS is used specifically 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
8
Q

What affects the NMR shift of the hydrogen atoms?

A

The atoms and groups next to the hydrogen. More electronegative shifts give a greater shift.

9
Q

What affects the splitting of a peak?

A

A the no. of hydrogen’s in a neighboring group plus one.

If a group has a neighboring hydrogen it will split into 2.

10
Q

what is the wavelength of uv light?

A

400 to 10 nm

11
Q

what is the wavelength of microwave radiation?

A

1mm to 1m

12
Q

what is the wavelength of waves in a microwave?

A

12.24 cm

13
Q

How does a microwave work?

A

The microwaves create an electric field and the polar water molecules try and line up with the field by rotating. This creates collisions and heat energy

14
Q

What are uses of microwaves other than to heat food?

A

Kill cancer cells

Dry wood paper and textiles as it is more efficient.

15
Q

What are the two different parts found in all chromatography?

A

mobile phase: where the molecules can move. Always liquid or gas.
Stationary phase: Where the molecules can’t move. Solid.

16
Q

How does gas chromatography work?

A

Thick liquid is the stationary phase and it covers the inside of a tube.
A gas or liquid sample is vaporised and put carried by a carrier gas, through the tube.
The tube is in a oven
Different parts of the sample are absorbed by the stationary phase by different amounts and so they all have different retention times.
The area under the graph produced gives relative amounts of each component.

17
Q

Explain HPLC

A

The stationary phase are small particles of solid (silica bonded to hydrocarbons) in a tube.
The polar mobile phase is a liquid (methanol and water) and it goes through the tube carrying the sample.
The retention time is measured by shining UV light through the mixture as it comes out.

18
Q

When can HPLC be used where GC can’t be?

A

As the substance isn’t heated in HPLC it can be used when the sample has a high boiling point or is heat sensitive.