Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > Analytical Techniques > Flashcards

Analytical Techniques Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Where are analytic techniques such as spectroscopy used?

A

In a wide range of analytical laboratories including forensic, public health and industrial

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does mass spectrometry provide information about?

A

Relative atomic mass and relative molecular mass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does high-resolution mass spectrometry enable?

A

Empirical formulae to be determined

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do fragmentation patterns in mass spectrometry provide?

A

Clues about the bonds and functional groups present which can be used to work out the structure of a substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

For simple quick and relatively inexpensive identification of functional groups what can be done?

A

Qualitative analysis using test tube reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do you test for alkenes?

A

Add dilute bromine solution which rapidly decoulorises when reacted with an alkene. This is because the bromine reacts with the c=c bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do you test for halogenoalkanes?

A
  • The carbon-halogen bond in a halogenoalkane I’d polar and susceptible to nucelophillic substitution. The hydroxide ion is a nucleophile. reaction with a halogenoalkane and a halide ion is one of the products formed
  • the halide ion can be identified using acidified silver nitrate solution followed by ammonia solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why are fluoroalkanes not detected when testing for a halogenoalkane?

A

Because they do not hydrolysed because the C-F bond is very strong and cannot be easily broken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the process of testing for a chloroalkane and what the results are

A
  • warm with dilute sodium hydroxide solution
  • add acidified silver nitrate solution: white precipitates of silver chloride form
  • add dilute ammonia solution followed by a concentrated ammonia solution: white precipitate dissolves conform a colourless solution when dilute ammonia is added
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the process of testing for a chloroalkane and what the results are

A
  • warm with dilute sodium hydroxide solution
  • add acidified silver nitrate solution: white precipitates of silver chloride form
  • add dilute ammonia solution followed by a concentrated ammonia solution: white precipitate dissolves conform a colourless solution when dilute ammonia is added
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe what the process of testing for a bromoalkane is and what the procedure is

A
  • warm with dilute sodium hydroxide solution
  • add acidified silver nitrate solution and a cream precipitate of silver bromide forms
  • add dilute ammonia solution, followed by concentrated ammonia solution and a cream precipitate dissolves to form a colourless solution only when concentrated ammonia is added
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the process of testing for an iodoalkane and what the result is

A
  • warm with dilute sodium hydroxide solution
  • add acidified silver nitrate solution and a yellow precipitate of silver iodide forms
  • add dilute ammonia solution followed by concentrated ammonia solution and the precipitate is insoluble in both dilute and concentrated ammonia solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the process of testing for an iodoalkane and what the result is

A
  • warm with dilute sodium hydroxide solution
  • add acidified silver nitrate solution and a yellow precipitate of silver iodide forms
  • add dilute ammonia solution followed by concentrated ammonia solution and the precipitate is insoluble in both dilute and concentrated ammonia solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the test you do to test whether something is a primary or secondary alcohol?

A

You add acidified potassium dichromate solution (VI). If it is a primary or secondary alcohol it will be oxidised to an aldehyde and the colour will change from orange to green. If it is a tertiary alcohol no reaction will take place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the test you do to test whether something is a primary or secondary alcohol?

A

You add acidified potassium dichromate solution (VI). If it is a primary alcohol it will be oxidised to an aldehyde and if it is a secondary alcohol it will be oxidised to a ketone and the colour will change from orange to green. If it is a tertiary alcohol no reaction will take place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What test do you do to distinguish between a primary and secondary alcohol?

A
  • Warm with Fehlings solution after it has been oxidised: a brick red precipitate will form if it is a primary alcohol and has been oxidised to an aldehyde. It will stay blue if it is a secondary alcohol oxidised to a ketone
  • warm with Tollens reagent:a silver mirror will form on the test tube if it is a primary alcohol and has been oxidised to an aldehyde. It will stay blue if it is a secondary alcohol oxidised to a ketone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do you test for a carboxylic acid?

A

Add sodium hydrogen carbonate solution and carbon dioxide will be given off. There will also be a low pH of the solution

18
Q

In qualitative tests what is it not necessary to do?

A

Measure volumes exactly

19
Q

Testing for an alkene involves adding bromine water. If the alkene is a liquid the two reagents can be added in equal volumes in a clean test tube. The mixture needs to be shaken. How do you do this?

A

Hold the test tube just below the lip and shake it with a jiggling motion

20
Q

How can you react an alkene gas with bromine water?

A

You can either bubble it through the bromine water or if it is collected in test tubes, bromine water can be added to the test tube and the test tube shaken

21
Q

How do you test the pH of a carboxylic acid?

A
  • Dip the end of a glass rod into the liquid, withdraw it with a drop of liquid clinging to it and touch this onto a piece of pH paper.
  • Use a pH probe
22
Q

How do you test for carbon dioxide given off after a carboxylic acid has reacted with a carbonate or hydrogen carbonate?

A

Use lime water

23
Q

When oxidising the alcohol what is the technique you carry out?

A

Add 1cm3 acidified potassium dichromate (VI) solution to the substance being tested, shake the test tube and then place it in a hot water bath for a few minutes

24
Q

How do you add fehlings solution to a sample being tested?

A

Add about 1cm3 of Fehling’s A and B solutions to a test tube. Add a few drops of the sample being tested. Fehlings solution is unstable so needs to be mixed right before. Then place the tube in a hot water bath for a few minutes

25
Q

What technique do you carry out when testing with tollens reagent?

A

Place 2cm3 of the sample being tested in a test tube and add about 5cm3 of tollens reagent. Leave at room temperature for a few minutes

26
Q

What can mass spectrometry be used for?

A
  • to determine the mass numbers of an elements isotopes and their relative abundance
  • to determine the relative molecular mass and the molecular formula of a compound
27
Q

A sample of ethanol injected into a time of flight mass spectrometer vaporises. In the ionisation area the gas is bombarded with a stream of electrons. What are the two possibilities?

A

• electrons are knocked off the molecules and positive ions form. Most molecules lose one electron. Ethanol molecules lose an electron to become [C2H5OH]+:
C2H5OH -> [C2H5OH]+
• some of the molecular ions break into smaller fragments. The charged fragments will also live through the spectrometer and produce lines in the spectrum.

28
Q

[C2H5OH]+ ions are the heaviest ions that can be produced from a sample of ethanol. What is the peak they produce on a mass spectrum called?

A

The molecular ion peak or parent ion because other molecular ions are made from it when it fragments in the mass spectrometer.

29
Q

What is the m/z value of the molecular ion peak?

A

The molecular mass of the compound

30
Q

Why cant you suggest the molecular formula of a molecule from the molecular ion peak using a low- resolution mass spectrometer?

A

Because there are several possible macular formulae for an particular mass both propane and ethanol have a relative molecular mass of 44

31
Q

Why can a high resolution mass spectrometer provide the information to work out the molecular formular of a compound?

A

It gives the relative isotopic masses to 6 significant figures so it allows an accurate identification of the molecular formula from the molecular ion peak

32
Q

What happens if infrared radiation is passed through a compound?

A

Some of the radiation is absorbed and some is transmitted

33
Q

What does infrared spectroscopy measure?

A

The wavelengths of infrared radiation that has been absorbed

34
Q

What is the infrared spectrum?

A

The chart that comes from the wavelength of infrared radiation. Wavelength is plotted along the x axis and the amount of radiation transmitted on the y axis

35
Q

What can infrared radiation be used to do?

A

Identify bonds in a compound

36
Q

In infrared spectroscopy you use wavenumber yo describe radiation. What is this and how can it be calculated?

A
  • it is the number of wave cycles per cm

* wavenumber= 1/ wavelength/cm cm-1

37
Q

What can the absorbances of the infrared spectrum be used to do?

A

Identify bonds and hence the functional groups in a molecule. Each bond will absorb a different wavenumber of radiation

38
Q

What is the fingerprint region.

A

The region of the infrared spectrum between 500 and 1500 cm-1

39
Q

What happens in the fingerprint region?

A

The wave numbers in this range are also absorbed by vibrations of the whole molecule in addition to the wave numbers absorbed by the C-C and C-O bonds thus means that this region of the infrared spectrum ie usually complicated with many absorptions

40
Q

What is the radiation transmitted from the sun to earth and what is the radiation emitted from the earth’s surface and what does it do?

A
  • sun to earth: UV

* earth: infrared. It warms earth as the greenhouse gases absorb it

41
Q

What means that greenhouse gases absorb infrared radiation?

A
  • The O-H bonds in water molecules strongly absorb infrared radiation at 3000-3800 cm -1
  • The C-H bonds in methane absorb infrared at about 3000 cm-1 (characteristic of all alkanes)
  • The C=O bonds in carbon dioxide absorb strongly at 2350 cm-1
42
Q

What happens as the concentration of greenhouse gases in the atmosphere increases?

A
  • infrared radiation absorbed by greenhouse gas molecules does not escape the atmosphere
  • as the concentration of greenhouse gases in the atmosphere increases the amount of infrared radiation being absorbed increases
  • this results in an increase in the kinetic energy of the molecules in the atmosphere which is detected as a temperature increase and referred to as global warming

Chemistry (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions