Chemical Analysis Flashcards
How do impurities affect the boiling point and melting point of a substance?
Boiling Point - increaces it
Melting Point - Decreaces it
For both, they widen the range of temperatures of which it will boil/melt
What is a formulation?
- A mixure of chemicals made to produce useful products.
- Each component plays a specific role in the formulation’s properties and must be in a precicely measured quantity
- examples include fuel, medicines, cleaning agents, fertilisers.
What is the mobile phase in chromatography?
What is the stationary phase in chromatography?
mobile phase - the solvent (e.g, water)
stationary phase - the solid or viscous liquid (e.g, the paper)
Recite the Rf value formula
distance travelled by substance / distance travelled by solvent
(MUST be under 1)
How does one test for hydrogen?
- place a LIT splint near the source that you wish to test
- in the presence of hydrogen, a squeaky pop will be heard
- this is because the hydrogen burns rapidly in the presence of oxygen, to produce H₂O
How does one test for oxygen?
- place a GLOWING splint near the source that you wish to test
- in the presence of oxygen, the splint will relight
How does one test for carbon dioxide?
- bubble limewater (calcium hydroxide) through the substance you wish to test
- in the presence of CO₂, the limewater will turn from colourless to cloudy
How does one test for chlorine?
- place (damp) litmus paper into the tube containing the substance you wish to test
- in the presence of chlorine, the litmus paper will go from red to white.
How do we test for the following metal ions?
Potassium (K⁺)
Copper (Cu²⁺)
Lithium (Li⁺)
Sodium (Na⁺)
Calcium (Ca²⁺)
- flame test
- when burned, these metal ions produce a characteristic colored flame:
Potassium (K⁺) - Lilac flame
Copper (Cu²⁺) - Green flame
Lithium (Li⁺) - Crimson flame
Sodium (Na⁺) - Yellow flame
Calcium (Ca²⁺) - Orangey-red flame
How does one undergo the flame test for metal ions?
(core practical)
- submerge the nichrome wire loop in dilute hydrochloric acid to steralise it
- place the nichrome wire loop into the sample that you wish to test
- hold the loop in a bunsen burner (on blue flame) and observe the change in the flame’s color
How are metal hydroxides formed?
metal ion + sodium hydroxide —> metal hydroxide
How can we differenciate between the following substances when reacted with sodium hydroxide?
- Copper (II)
- Iron (II)
- Iron (III)
- Calcium hydroxide
- Magnesium hydroxide
- Aluminium hydroxide
- Copper (II) forms a blue precipitate
- Iron (II) forms a green precipitate
- Iron (III) forms a brown precipitate
- Calcium ions form a white precipitate
- Magnesium ions form a white precipitate (must be burned to be distinguished between calcium hydroxide)
- Aluminium ions form a white precipitate, but in the presence of excess white precipitate, will dissolve into a colorless solution.
How does one test for a carbonate ion?
- add dilute acid to the sample, you will observe fizzing. water, carbon dioxide and a salt would be produced.
- bubble the gas through limewater. If it goes cloudy, it shows the presence of carbon dioxide, which means you have started with a carbonate ion.
What is a halide ion and how do you test for it?
A halogen with a negative charge (e.g, flourine, chlorine, bromine, iodine)
- add dilute nitric acid (this removes carbonate ions that could form a different pricipitate with the silver nitrate)
- add silver nitrate solution
- obeserve the precipitate colour
- flourine - no precipitate
- chlorine - white precipitate
- bromine - cream precipitate
- iodine - yellow precipitate
How do we test for sulfates?
- Add dilute hydrochloric acid (this removes carbonate ions that could disrupt the test by forming their own precipitate)
- add barium chloride solution. in the presence of sulfates, this forms a white precipitate.
