Question | Answer |
What is the difference between quantitative and qualitative data analysis? | •Qualitative analysis is the investigation into the kind of substances present in an unknown sample
•Quantitative analysis the investigation into the amount/mass/volume of each substance present in an unknown sample |
Why must the test for any ion be unique? | The test for any ion must be unique so the presence of each ion can be identified correctly |
How can cations be tested for? | A few drops of sodium hydroxide solution are added to a solution of the unknown substance as many metal hydroxides are insoluble, so a precipitation reaction can occur
Precipitates
*Al3+ = white
*Ca2+ = white
*Cu2+ = pale blue
*Fe3+ = brown |
How can calcium and aluminium ions be distinguished from each other when a sodium hydroxide solution is added to them? | add excess sodium hydroxide solution: the aluminium ion precipitate will redissolve to form a colourless solution, but the calcium ion precipitate will not change |
How can halide ions be tested for? | To test for halide ions, add silver nitrate solution and dilute nitric acid to the halide ion solution
*Chloride - Cl- = white precipitate
*Bromide - Br- = cream precipitate
*Iodide - I- = yellow precipitate |
How can you test for ammonium ions? | Ammonium ions can be detected by heating the unknown substance with sodium hydroxide solution, as if ammonium is present it will give off a smelly, alkaline gas, and will turn damp red litmus paper blue |
What is an ionic equations - when are they used, how are they formed? | Equations involving reactants that are solutions can form ionic equations. All solutions are split up into ions, as the ions can move around independently in solutions. The ions that do not change in the reaction are omitted from the equation |
Turn this equation into an ionic equation: AgNO3 (aq) + KCl (aq) -> AgCl (s) + KNO3 (aq) | Ag+ (aq) + Cl- (aq) -> AgCl (s) |
What are ion tests used for? | • Checking purity of drinking water
• Water treatment (chlorine, aluminium salts and sodium fluoride)
• Checking presence of substances in the blood- iron + anaemia, sodium ions + high blood pressure and kidney disease, aluminium + Alzheimer’s disease |