C12 - Chemical Analysis Flashcards
What is a pure substance?
A substance made up of only one specific substance, whether it be element or compound.
How are substances tested for purity?
The melting and boiling points of a substance are fixed, so this can be used to test a substance’s purity. Generally, impurities lower melting point and raise boiling point of a substance.
What is a formulation?
A mixture that has been designed to produce a useful product for a specific use, e.g. medication.
How are chromatogram results presented?
As a Rf value - retention factor. Worked out using Rf = distance moved by substance / distance moved by solvent.
How are Rf values used?
Rf values are stored in databases, so unknown chemicals found in other chromatograms can be compared to a database to ID the chemical.
How are gases collected for testing?
Boiling tube placed over test tube, then turned over to perform test.
How is hydrogen tested for?
Lit splint held at end of test tube - splint “pops”.
How is oxygen tested for?
Glowing splint held in test tube - splint relights.
How is carbon dioxide tested for?
Bubble gas through limewater (calcium hydroxide solution) using a test tube with a glass straw - limewater turns cloudy.
How is chlorine tested for?
Dampened blue litmus paper held at end of test tube - turns white, gets bleached.
What are the results for flame tests with lithium?
Crimson.
What are the results for flame tests with sodium?
Yellow.
What are the results for flame tests potassium?
Lilac.
What are the results for flame tests with calcium?
Orange-red.
What are the results for flame tests with copper?
Green.
What materials can be tested for with sodium hydroxide?
Copper2+, Iron2+, Iron3+, Aluminium3+, Mg2+, Ca2+.
What is the testing process with sodium hydroxide?
https://cdn.discordapp.com/attachments/303250641575215115/414766076845359105/unknown.png
How are carbonates tested for?
Adding a dilute acid to a carbonate, then bubbling the gas produced through limewater - limewater turns cloudy if positive.
How are halides (chlorides, bromides, iodides) tested for?
Adding nitric acid, then silver nitrate solution. If solution is yellow, iodide is positive. If solution is cream, bromide is positive. If solution is white, chloride is positive.
How are sulfates tested for?
Adding hydrochloric acid, then barium chloride solution. If solution turns white, sulfate is positive.
What is instrumental analysis?
Instrumental analysis is using special machines and technology to test materials, instead of a practical experiment.
What are the advantages and disadvantages of instrumental analysis?
+ Highly accurate.
+ Quick.
+ Allow very small samples to be analysed.
- Very expensive.
- Requires special training.
- Gives data that can only be compared with other known substances.
What is flame emission spectroscopy?
Heating a sample in a flame, then shining the light produced against a white sheet, then using the spectogram shown to identify the components of the sample. It can also show the concentration of the metal ions in a solution.
