Percentage Yield and Chemical Analysis Flashcards
Why is percentage yield never 100%?
- Reversible reactions
- Filtration
- Unexpected reactions
Why do reversible reactions mean the percentage yield is never 100%?
Some of the products are always reacting together to change back to the original reactants.
Why does filtration mean the yield is less than 100%?
Some of the product is lost when it’s separated from the reaction mixture.
What is sustainable development?
Making sure we don’t use resources faster than they can be replaced.
What is an example of sustainable development?
Using as little energy as possible to create highest product yield possible.
How can artificial colours be separated?
Paper chromatography.
What are examples of artificial colours?
Food colouring or dyes.
Why could four spots on a chromatogram not mean four dyes?
Two dyes make a spot in the same place.
What are the advantages of using machines to analyse substances?
- Very sensitive (even tiny substances)
- Very fast (automated too)
- Very accurate
What is gas chromatography used for?
Separate out a mixture of compounds and help to identify the substances present.
Why are substances separated by gas chromatography?
The substances travel through the tube at different speeds.
What is the retention time?
The time taken for the gases to reach the detector.
How can a mass spectrometer be used?
To identify the substances leaving the column.
What is GC-MS?
Gas Chromatography Mass Spectrometer
Why must a pencil be used to draw a baseline, instead of a pen?
Pen ink could dissolve in the solvent.
