C12 Flashcards
What is a pure substance?
One that is just made of one element or compound.
How can you identify a pure substance?
If there is one exact melting or boiling point it is a fixed point and it is pure.
How to tell if something is impure?
If there is a range for the melting and boiling points.
What is a formulation?
A mixture that has been designed to produce a useful product.
What is the mobile and stationary phase?
The mobile phase moves through the stationary phase, carrying the mixture with it.
How to calculate the Rf value?
Distance moved by substance/distance moved by solvent.
What is the test for hydrogen?
Put a lit splint inside a test tube full of hydrogen gas and a squeaky pop will occur.
What is the test for carbon dioxide?
Bubble carbon dioxide gas through limewater and it will turn cloudy.
How to test for oxygen?
Put a glowing splint inside a test tube full of oxygen and it should relight.
What is the test for chlorine gas?
Turns damp blue litmus paper bleached white.
What are the flame tests for Lithium, Sodium, Potassium, Calcium and Copper.
Lithium-crimson
Sodium-yellow
Potassium-lilac
Calcium-yellow red
Copper-green
What do aluminium, calcium and magnesium ions for with sodium hydroxide?
White precipitates.
Ionic equation for metal cation tests with sodium hydroxide:
Al3+ + 3OH- = Al(OH)3
What do copper (II), iron(II) and iron(III) ions form with a sodium hydroxide solution?
Copper(II)-blue precipitate
Iron(II)-green precipitate
Iron(III)-brown precipitate
How can a carbonate be identified?
By adding a dilute acid, producing carbon dioxide gas which then turns limewater milky if bubbled through.
What does a carbonate and an acid produce?
Carbon dioxide and water
How can you identify halide ions?
Add dilute nitric acid then a silver nitrate solution. If a precipitate forms, there are halide ions present.
What colour does the precipitate turn with iodide, bromide and chloride ions?
Iodide ions-yellow precipitate
Bromide ions-cream precipitate
Chloride ions-white precipitate
How to test for sulfate ions?
Add dilute hydrochloric acid followed by barium chloride solution. This gives a white precipitate if they are present
What are the benefits of using instrumental methods?
They are highly accurate and sensitive, they are quicker and enable very small samples to be analysed.
What are the disadvantages of instrumental methods?
The machinery is expensive, takes specialist training to use and gives results that can only be interpreted with other given data from known substances.
What is flame emission spectroscopy?
An example of an instrumental method, which tells us which metal ions are present from their lines and also tells us the concentration of the metal ions.
