Unit 3: Section 4- Organic Analysis + RP6

Question 1

What can a mass spectrum show?

Answer 1

the whole molecule and fragments of a molecule

Question 2

Define molecular ion

Answer 2

the molecule with one electron
knocked off (It is both an ion and a free radical)

Question 3

What can high resolution mass spectrometers be used to determine?

Answer 3

the molecular formula of a compound
they can help differentiate between compounds that appear to have similar Mr

Question 4

How many peaks on a mass spectroscopy will chlorine and bromine produce and why?

Answer 4

2 because they have 2 naturally occurring isotopes

Question 5

What importance does 1500cm-1 have in infrared spectrscopy?

Answer 5

above- functional group identification
below- ‘fingerprinting’

Question 6

Describe the fingerprinting region of infrared spectroscopy

Answer 6

complicated
unique for every compound

Question 7

Why can infrared spectroscopies identify molecules?

Answer 7

because certain groups in a molecule absorb infra-red radiation at characteristic frequencies

Question 8

What can infrared spectroscopies be used for?

Answer 8

they can identify functional groups
they can identify impurities
fingerprinting

Question 9

Describe O-H absorptions

Answer 9

tend to be broad

Question 10

What can rouge absorptions indicate?

Answer 10

impurities

Question 11

Describe the mechanism of the greenhouse effect

Answer 11

UV wavelength radiation passes through the atmosphere to the Earth’s surface and heats up Earth’s surface.
The Earth radiates out infrared long wavelength radiation.
The C=O Bonds in CO2
absorb infrared radiation so the IR radiation does not escape from the atmosphere.
This energy is transferred to other molecules in the atmosphere by collisions so the atmosphere is warmed.

Question 12

RP 6- Describe the test and result for an alkene

Answer 12

Bromine water
orange solution decolourises

Question 13

RP 6- Describe the test and result for an aldehyde with Fehling’s solution

Answer 13

Conditions: heat gently
Reaction: aldehydes only are oxidised by Fehling’s Solution
into a carboxylic acid. The copper (II) ions are reduced
to copper(I) oxide .
Observation: Aldehydes :Blue Cu 2+ ions in solution change to
a red precipitate of Cu2O. Ketones do not react

Question 14

RP 6- Describe the test and result for an aldehyde with tollen’s reagent

Answer 14

Conditions: heat gently
Reaction: aldehydes only are oxidised by Tollens’ reagent into a carboxylic acid. The silver(I) ions are reduced to silver atoms
Observation: with aldehydes, a silver mirror forms coating the inside of the test tube. Ketones result in no change.

Question 15

RP 6- Describe the test and result for a 1o 2o alcohol and aldehyde

Answer 15

sodium dichromate and sulphuric acid
orange to green colour change

Question 16

RP 6- Describe the test and result for a chloroalkane

Answer 16

warm with silver nitrate
slow formation of white precipitate of AgCl

Question 17

What is the purpose of mass spectrometry?

Answer 17

identify an unknown compound

Question 18

What does mass spectrometry measure?

Answer 18

mass-to-charge ratio of ions

Question 19

What is the definition of a molecular ion?

Answer 19

electrons are removed from an organic molecule to form a positive ion

Question 20

What is the symbol for a molecular ion?

Answer 20

M+

Question 21

What is the charge of a molecular ion?

Answer 21

positive

Question 22

What is a feature of a molecular ion?

Answer 22

unstable

Question 23

What type of radiation is used for infrared spectroscopy?

Answer 23

infrared radiation

Question 24

What units are used during infrared spectroscopy?

Answer 24

cm-1