validation (emission and absorption spectrum)

Question 1

sodium

Answer 1

yellow

Question 2

potassium

Answer 2

lilac

Question 3

calcium

Answer 3

red

Question 4

copper

Answer 4

green

Question 5

limitations of flame test

Answer 5

• qualitative data only
• low conc of metals are hard to observe
• colours are subjective
• only a few metal ions can be detected
• mixtures of metals produce confusing results

Question 6

spectroscopy

Answer 6

the study of the interaction between matter and electron magnectic radiation

Question 7

what components of the salts is responsible for the colours observed?

Answer 7

metal ions

Question 8

what assumption is made about the ethanol in the flame test?

Answer 8

that ethanol has a colourless flame and that it doesn’t effect the colour of the flame for accurate results

Question 9

why must a clean watch glass be used for each test

Answer 9

so theres no contamination which can effect the result of the flame

Question 10

Explain how the coloured light observed is produced

Answer 10

• When the metal ion in the salt is given heat (energy) the electrons becomes excited
• the electrons absorbs the energy and moves up an energy level (electron shell)
• this is very unstable
• when the electrons return to ground state the same energy absorbed is released in form of wavelengths (light)

Question 11

Give a practical use of this type of the flame test

Answer 11

To identify and determine unknown metal ions

Question 12

Often different colours are used to describe the same flame colour, e.g. lilac, mauve or purple for potassium.
Why might this be a problem?

Answer 12

Different people may have different opinions on the same flame colour. Therefore results are subjective.

Question 13

Is this a random or systematic error? Justify your choice.

Answer 13

systematic because one individual will always identify and observe the same colour the same way in every test

Question 14

explain how emission spectra provide evidence for electron shells in the Bohr model

Answer 14

• Bohrs model explained that these light emissions were able to identify that electrons in atoms can only be found at certain energies
• these engeries associate with the shells the electrons can be found in

Question 15

why do we see lines in an emission spectrum are different colours

Answer 15

• when atoms are heated to an excited state & its valence elections jump to a higher energy level
• moments later as it returns to its original ground state
  it will emit a colour of light with an energy that perfectly corresponding to the energy difference

Question 16

does a sodium ion(2,8) and a neon atom (2,8) display the same emission spectra

Answer 16

no although they share the same electron configuration, they differ in charges in the nucleus and electrons

Question 17

advantages of flame test

Answer 17

provides a quick analysis of the chemical composition of a sample

Question 18

in AAS, what is the source of the energy that excites the atom in the sample being analysed

Answer 18

the light source that produces light characteristic of the metal being analysed

Question 19

advantages of AAS over flame test

Answer 19

AAS:

• provides both a qualitative and quantitative test
• can detect elements in low conc
• is highly selective and is regularly used with mixtures

Question 20

strontium

Answer 20

Scarlett

Question 21

why do we see colour from the flame test

Answer 21

when unstable/excited electrons ‘fall’ back down to the ground state, they will all release the same amount of energy and therefor all produce the same wavelength of light

Question 22

absorption spectra

Answer 22

electrons are able to absorb electromagnetic radiation and move to a higher energy level

Question 23

Absorption lines are …

Answer 23

black
- the missing colours correspond to the exact quantity of energy required to promote valence electrons to a higher energy level

Question 24

emission lines are …

Answer 24

coloured

- light emitted by the element can be separated into its wavelength components