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Flashcards in EMR/UV-Vis Deck (27):
1

Light waves are electromagnetic. True or false?

True

2

How is the speed of light calculated?

Wavelength x frequency

3

On absorption of radiation, electrons are promoted from a low energy state to a higher energy (excited state). True or false?

True

4

EMR is produced when excited particles return to lower-energy levels or the ground state. True or false?

True

5

Excitation of a molecule can be electronic, rotational or vibrational. True or false?

True

6

What is on the y and x axis of UV-Vis spectrums?

y - absorbance
x - wavelength

7

Most drugs, with the exception of _______ ones absorb UV light

coloured

8

Why is the UV-vis spectrum broad rather than sharp?

Because photons with slight difference in energy can still cause electronic transitions from exciting electrons from the many vibrational states

9

What are the three types of orbitals?

sigma
pi
n - non-bonding

10

When a bonding orbital is created, there is also an anti-bonding orbital created that is normally unoccupied but lies at a higher or lower state?

Higher (less stable) state

11

On energy level diagram, jumps from which two states are in low enough energy for pharmaceutical analysis?

pi to pi*
and n to pi*

12

>200nm absorption is most common for pharmaceutical analysis. True or false?

True

13

What are the 3 uses of UV absorption?

Identification of drugs - by comparing spectra
Measuring reactions, ionisation
Quantification of drugs - most useful

14

UV absorption is mostly restricted to drug molecules with conjugated bonds. True or false?

True

15

What is meant by a conjugated structure?

Double bonds alternating with single bonds

16

Conjugated structures tend to shift absorption to a shorter wavelength. True or false?

False - longer wavelength

17

What is meant by a bathochromic shift?

shift to a longer wavelength

18

The longer the conjugated system, the less separation in energy levels and therefore the longer the wavelength. True or false?

True

19

Bathochromic is a red shift. True or false?

True

20

What colour is associated with a hypsochromic shift?

Blue

21

Why does conjugation shift the wavelength to red?

Because in conjugated systems, electrons are easily delocalised, making energy gaps between orbitals smaller, therefore lowering the energy needed to excite them

22

What is an auxochrome?

A functional group containing lone pair(s) of electrons that do not absorb appreciable amounts of UV on its own but shifts peaks to longer wavelength and makes the peak higher intensity

23

What is a chromophore?

Part of the molecule that absorbs UV or visible light

24

The amount of light absorbed is dependent on the concentration of a sample. True or false?

True

25

What is the equation for the Beer lambert law?

A = Ebc
E = molar absorptivity (absorbance of 1M solution)
b = path length of cell in cm
c = conc in mol/l

26

What does the beer lambert law apply?

A linear relationshop between absorbance and concentration. However, in reality, this is only true if A > 1.5

27

In the beer lambert law, what assumptions apply for absorbance to be directly proportional to concentration?

Incidence radiation must be monochromatic
absorbance checks can be made against standards such as potassium dichromate
each molecule in solution acts as an independent absorbing species
absorption takes place in a homogenous solution