Chemical Analysis Flashcards
(15 cards)
What is chromatography?
A technique used to separate mixtures due to the distribution of the substances between the stationary and mobile phase. It can give information to help identify substances.
What is a formulation?
A mixture that has been designed as a useful product. They are made by mixing the components in carefully measured quantities to ensure that the product has the required properties.
What is an impure substance?
A substance made up of two or more elements or compounds that are not bonded together chemically.
What is litmus paper?
Paper stained with litmus which can be used to indicate the acidity or alkalinity of a substance. Used in the test for chlorine.
What is the mobile phase in chromatography?
Where the molecules can move during chromatography. It is always a liquid or gas.
What is precipitation?
The creation of a solid from a solution.
What is a pure substance?
In chemistry, a pure substance is a single element or compound, not mixed with any other substance. it can mean a substance that has had nothing added to it, so it is unadulterated and in its natural state.
Has very specific boiling and melting points
What is the Rf value?
The ratio of the distance moved by a compound to the distance moved by the solvent.
What is the stationary phase in chromatography?
Where the molecules are stationary during chromatography. It is a solid or a liquid supported on a solid.
Give 3 examples of a formulation
- Medicines – e.g. Paracetamol tablets
- Paint
- Alloys – e.g. Steel
How does chromatography work
- A pencil line is drawn near the bottom of the chromatography paper.
- Samples (e.g. inks or dyes) are placed as spots on the pencil line.
- The bottom of the paper is placed in a solvent (e.g. water or ethanol), below the line.
- The solvent moves up the paper by capillary action.
- Different substances move up at different speeds, separating based on their solubility.
- The result is a chromatogram, showing how many substances are present by the number of spots.
How do you test for hydrogen gas?
Put a lit splint in the test tube — it makes a squeaky pop.
How do you test for oxygen gas?
Put a glowing splint in the gas — it will relight.
How do you test for carbon dioxide?
Bubble it through limewater — the limewater turns cloudy.
How do you test for chlorine gas?
Hold damp blue litmus paper in the gas — it turns red then white (bleached).
