SC25-26 Flashcards
What are flame tests used for?
To identify metal ions.
How do you carry out a flame test?
- First clean a nichrome wire loop by dipping it into hydrochloric acid and then rinsing it in distilled water.
- Then dip the wire loop into a sample of the metal compound and put the loop in the clear blue part of a Bunsen flame.
- Record the colour the flame goes.
What flame does- Lithium Sodium Potassium Calcium Copper - ion give off
Lithium - red Sodium - yellow potassium - lilac Calcium - orange/red Copper - blue/green
How can flame tests be inaccurate?
Different metal ions may give a similar colour, so hard to distinguish.
Machines are more accurate and sensitive. A flame photometer can measure light intensity.
How can you identify dissolved metal ions?
Precipitate reactions involving dilute sodium hydroxide (NaOH) solution.
How do you carry out a precipitate reaction?
- You just add a few drops of sodium hydroxide solution to a solution of your mystery compound.
- If a hydroxide precipitate forms, you can use its colour to tell which metal ion was in the compound.
What is the colour of precipitate for - Aluminium Calcium Copper Iron (ll) Iron (lll) - ions?
Aluminium - white Calcium - white Copper - blue Iron (ll) - green Iron (lll) - brown
How do you know if the ion is aluminium or calcium in a precipitate reaction?
Keep adding sodium hydroxide.
Aluminium will go colourless.
How do you test for carbonate ions?
- Add dilute HCL to the solid or solution and look for bubbles of carbon dioxide being produced.
- The gas can be identified as carbon dioxide by bubbling through limewater.
How do you test for sulfate ions?
- Add dilute HCL to remove any carbonate ions.
- Add barium chloride solution.
- The presence of sulfate ions is shown by a white precipitate of barium sulfate.
How do you test for negative ions/halide ions?
Chloride, bromide, iodide
- Add a few drops of dilute nitric acid to remove any carbonate ions.
- Add a few drops of sliver nitrate solution.
In the test for halide ions what colour does - Chloride Bromide Iodide - go?
Chloride - white
Bromide - cream
Iodide - yellow
What are nanoparticles?
Really small particles.
What are some features of nanoparticles?
Have huge SA:VR
Not visible to the eye.
They’re structure, 1-100 nanometers in size, that usually contain only a few hundred atoms.
100 times larger than atoms and simple molecules.
They’re smaller than cells.
What is an example of a nanoparticle?
Fullerenes.
What are bulk materials?
Lumps and powders.
They consist of huge numbers of atoms.
How do you work out the surface area to volume ratio?
= surface area / volume
What are some uses of nanoparticles?
Sunscreen Catalyst Nano-medicine Lubricant coatings In electrical circuits Sports equipment Clothing (socks)
Why are nanoparticles used in sunscreen?
The small particles provide better protection but don’t leave white marks on the skin (invisible sunscreen).
Nanoparticulate titanium dioxide is transparent because it’s particles are so small, but it still absorbs ultraviolet radiation.
Why are nanoparticles used as catalysts?
Because of their large SA:VR.
Stain resistant clothes treated with nanoparticulate materials stay clean because nanoparticles catalyse the breakdown of dirt.
Why are nanoparticles used in nano-medicine?
Fullerenes - deliver drugs right to the cells where they’re needed.
Why are nanoparticles used in sports equipment?
They’re added to plastics (tennis rackets, golf clubs and balls.
They make the plastic much stronger and more durable, without adding noticeable mass.
Why are nanoparticles used in clothing?
Antibacterial socks -
Silver kills bacteria. They’re more affective at killing bacteria because of their large SA:VR.
Silver nanoparticles can be woven into the fabric used to make socks. The silver kills bacteria and helps stop them coming back.
What are the risks of nanoparticles?
- Pose hazard to human health and the environment - don’t know the side effects.
- Sample size allows them to be inhaled, or pass through cell surface membrane.
- The large SA:VR could allow them to catalyse harmful reaction, or to carry toxic substances bound to their surfaces.
- The risks are difficult to be determined because they haven’t been around for long.
