Tests for Ions - Quantitive analysis

Question 1

how do you carry out the flame test

Answer 1

• clean wire loop
• dip into HCL
• dip into metal compound and put on blue part of bunsen burner

Question 2

why the test for any ion must be unique

Answer 2

Two or more ions means the colours will mix, making identification erroneous

Question 3

why shouldn’t u make bunsen burner too hot

Answer 3

Avoid letting the wire get so hot that it glows red otherwise this can be confused with a flame colour

Question 4

what colour does lithium give off
what colour does sodium give off
what colour does potassium give off
what colour does calcium give off
what colour does copper give off

Answer 4

• red
• yellow
• lilac
• orange/red
• blue/green

Question 5

how can you identify metal from aqueous solutions

Answer 5

• adding sodium hydroxide and identify colour of precipitate

Question 6

what colour does aluminium give off
what colour does calcium give off
what colour does copper give off
what colour does iron II give off
what colour does iron III give off

Answer 6

• white but when redissolved w excess NAOH form colourless
• white
• blue
• green
• brown

Question 7

how can you figure out if ammonia is present

Answer 7

• add sodium hydroxide and heat
• place red litmus paper if turn blue alkali so ammonia
• strong smell but toxic and irritant

Question 8

what is the test for halide ions

Answer 8

• first add nitric acid to halide then silver nitrate

Question 9

why should you add nitric acid before silver nitrate

Answer 9

to remove any carbonate ions which would produce a precipitate of silver nitrate confusing results.

cannot use hydrochloric acid as already adding to chloride

Question 10

what colour is given off in
chloride
bromide
iodide

Answer 10

• white
• cream
• yellow

Question 11

test for carbonate

Answer 11

Add dilute acid and test the gas released.

Effervescence should be seen and the gas produced is CO2 which forms a white precipitate of calcium carbonate when bubbled through limewater:

Question 12

what is test for sulfate ions

Answer 12

dilute hydrochloric acid and add aqueous barium chloride.

A white precipitate of barium sulfate is formed

Question 13

what are the advantages of instrumental

Answer 13

• Modern instruments are very sensitive and can work with very small sample sizes
• They are faster and easier to use
• They provide greater accuracy

Question 14

what is flame photometry

Answer 14

• instrumental method which allows u to identify ions, measure intensity and wavelength which produce line spectrum and can be used to work out concentration on calibration curve

Question 15

how is flame photometry better than flame tests

Answer 15

• works with mixtures as compare it to reference spectra