SC25a Flame Tests and Photometry

Question 1

steps to carry out a flame test

Answer 1

~light a bunsen burner and open air hole to give a roaring flame
~pick up a small sample of the test substance using a wire loop
~hold sample in the edge of the flame and observe flame colour
~dip loop in water to cool
~dip loop in HCl to clean

Question 2

lithium flame test colour?

Answer 2

crimson

Question 3

sodium flame test colour?

Answer 3

yellow

Question 4

potassium flame test colour?

Answer 4

lilac

Question 5

calcium flame test colour?

Answer 5

orange - red

Question 6

copper flame test colour?

Answer 6

green

Question 7

advantages of using scientific instruments rather than flame tests? 3

Answer 7

~accuracy
~speed
~sensitivity

Question 8

what is used in a lab instead of flame tests?

Answer 8

flame photometry - machines that analyse substances

Question 9

how does a flame photometer work?

Answer 9

measures the light intensity of the flame colours produced by metal ions

Question 10

calibration curves?

Answer 10

graphs that are produced using different standard solutions of the metal ion dissolved in distilled water

Question 11

explain why a flame test could not be used to identify the metal ions in a mixture of lithium chloride and calcium chloride? 2 marks

Answer 11

~lithium ions give a red flame whilst calcium ions give a orange red flame so hard to distinguish
~one colour hides the other colour/the 2 colours mix together

Question 12

how can a metal ion in a unknown solution be identified?

Answer 12

a flame photometer can separate out these colours to produce a spectrum of the light emitted by each metal ion and is later identified by matching its spectrum from a known metal ion