| How can I test for metal ions? | Add dilute sodium hydroxide
Dilute sodium hydroxide solution reacts with the solution of the metal to form coloured insoluble metal hydroxides |
| How do you carry out the flame test? | 1)dip a clean wire loop into a solid sample of the compound being tested
2)put the loop into the edge of the blue flame from a Bunsen burner
3)observe and record the flame colour produced |
| What are the colours for each flame Lithium, Sodium, Potassium, Calcium, Copper | Lithium, Li+ Crimson
Sodium, Na+ Yellow
Potassium, K+ Lilac
Calcium, Ca2+ Orange-red
Copper, Cu2+ Green |
| What colours do aluminium, calcium, magnesium, copper, iron (Fe2+) and iron (Fe3+) metal hydroxides form? | Aluminium, Al3+ White
Calcium, Ca2+ White
Magnesium, Mg2+ White
Copper(II), Cu2+ Blue
Iron(II), Fe2+ Green
Iron(III), Fe3+ Brown |
| What happens if there is excess sodium hydroxide? | 1)the aluminium hydroxide precipitate dissolves to form a colourless solution
2)the calcium hydroxide precipitate is unchanged
3)the magnesium hydroxide solution is unchanged |
| What are the 3 negatively charged ions to test for? | Sulphate ions, carbonate ions and halide ions |
| How do we test for negatively charged ions? | Testing for carbonate ions:
dilute acid usually hydrochloric added to the compound, bubbles are given off caused by carbon dioxide
Testing for sulfate ions:
add a few drops of hydrochloric acid to remove the carbonate ions, then add a few drops of barium chloride solution, white barium precipitate forms
Testing foe halide ions:
add a few drops of dilute nitric acid to the sample to remove carbonate ions then add a few drops of dilute silver nitrate solution the halides form these precipitates:
Chloride, Cl- White
Bromide, Br- Cream
Iodide, I- Yellow |
| What is flame emission spectroscopy? | A scientific instrument based on flame testing its used to (1)identify metal ions in a sample (2)determine the concentration of metal ions in dilute solutions |
| Why is flame emission spectroscopy better than using a test in a lab? | 1)speed
2)accuracy
3)sensitivity (detect very small amounts of sample) |
| How do we identify metal ions using a spectroscope? | In the flame emission spectroscope, the coloured light from a vaporised sample can be split to produce an emission spectrum. The different lines in an emission spectrum look like a coloured barcode. Each metal ion produces a unique emission spectrum.
The metal present in a sample is identified by comparing its spectrum with reference spectra. These are emission spectra from known metal ions. If two spectra match, they must be from the same metal ion. |
