C12-chemical Analysis Flashcards
Pure in advertising
Nothing added to it
Pure in chemistry
A pure substance is one that is made up of just one substance. That’s substance can be either an element or a compound.
What can you use to identify pure substances?
Boiling and melting points (of an element or compound are called fixed points)
What do impurities tend to do?
Lower the melting point of a substance and raise its boiling point
What is a formulation?
Is a mixture that has been designed to produce a useful product
What is the Rf formula
Distance moved by substance/ distance moved by solvent
How do you test for hydrogen?
The reaction between zinc and dilute acid is a convenient way to make some hydrogen gas to test.
Hold a lighted splint at the open end of the test tube of hydrogen gas
A lighted splint pops
Few crystals of copper sulfate act as a catalyst
How to make oxygen
Hydrogen peroxide with magenese oxide as a catalyst makes water + oxygen
How to test for oxygen?
A glowing splint relights
How do you make carbon dioxide?
By reacting calcium carbonate and dilute hydrochloride acid to make calcium chloride + water + carbon dioxide
How to test for carbon dioxide
Bubble carbon dioxide gas through like water (calcium hydroxide solution)
Lime water turns cloudy white
Testing for chlorine gas
Add concentrated hydrochloric acid to a spatula of moistened potassium manganate crystals in a boiling tube held in a rack inside a fine cupboard
Damps blue litmus paper turns white as it gets bleached
How to do the flame test?
Nichrome wire loop should be dipped in concentrated hydrochloric acid and then heated to clean it first. Dipped in the acid again before dipping it into the metal compound.
Thé. Hold the loop in the roaring blue flame of a Bunsen burner
Metal ions for Crimson Yellow Lilac Orange red Green
Lithium Li+ crimson Sodium Na+ yellow Potassium k+ lilac Calcium Ca2+ orange red Copper cu 2+ green
How to test for positive ions
Add sodium hydroxide solution
What do magnesium calcium and aluminium all form when a sodium hydroxide is added
A white precipitate
What redissolves when add excess sodium hydroxide solution
Aluminium precipitate
How can calcium and magnesium ions be distinguished?
Flame test
Calcium orange red
Magnésium no colour at all
Coloured precipitates
Copper II ions a blue precipitate
Iron II ions a green precipitate
Iron III a brown precipitate
Test for carbonate ion
Add dilute acid
Acid will react with the carbonate to make carbon dioxide gas see fizzing
Magnesium carbonate + hydrochloric acid makes magnesium chloride + water + carbon dioxide
Test for halide ions
Add dilute nitric acid to the sample
Add dilute silver nitrate solution
Valide ions produce a precipitate of silver halide
Precipitate colours
Chloride ions
Bromide ions
Iodide ions
White precipitate Cream precipitate Yellow precipitate Silver chloride Silver bromide Silver iodide
Test for sulfate ions
Add dilute hydrochloric acid
Add barium chloride solution
Sulfate ions are présent you will see a white precipitate
