Chemistry GCSE AQA- Chemical analysis

What does pure mean?

A substance that only contains one type of element or compound

Pure substances do what over a range of temperatures?

Change state

What is the name of the one temperature that pure substances melt and solidify at?

Melting point

What is the name of the one temperature that pure substances boil and condense at?

Boiling point

What is a formulation?

Mixtures that have been designed to have specific properties

What is the name of the stage in chromatography that doesn't move?

Stationary phase

What is the name of the stage in chromatography that does move?

Mobile phase

In paper chromatography, what is the stationary phase?

The paper

In paper chromatography, what is the mobile phase?

The solvent (water)

What happens during chromatography?

Mixtures separate into their components

Why do the components separate in chromotography?

They move a different distance depending on its attraction for the paper and solvent

What can chromatography be used for?

To identify artificial colours (in food) by comparing it with results from known substances

What is the equation for the Rf value?

Distance moved by substance/distance moved by solvent

What is the Rf value used for?

To identify the component

What are the properties of hydrogen?

Colourless, combines violently with oxygen when ignighted

What is the test for hydrogen?

Lit splint and burns with squeaky pop

What are the properties of chlorine?

A green, poisonous gas that bleaches dyes

What is the test for chlorine?

Turns damp red litmus paper white

What are the properties of oxygen?

A colourless has that helps fuels burn more readily than in air

What is the test for oxygen?

Relights a glowing splint

What are the properties of carbon dioxide?

A colourless gas

What is the test for carbon dioxide?

Turns limewater cloudy when bubbled through it

What are instrumental methods?

Standard lab equipment is used to detect and identify substances

What is flame emission spectroscopy used for?

To identify metal ions in a substance which contains more than 1 ion

How does emission spectroscopy work?

The metal solution is placed in a flame and the light emitted is passed through a spectroscope

What can the line spectrum produced by a substance in emission spectroscopy be used for?

Identifying ions, measuring the concentration of the metal ions

What are flame test used for?

To identify a metal ion in a substance that contains only 1 ion

What colour does copper go in a flame test?

Green

What colour does calcium go in a flame test?

Brick red

What colour does lithium go in a flame test?

Crimson red

What colour does potassium go in a flame test?

Lilac

What colour does sodium go in a flame test?

Yellow

What problem occur in flame test if a sample contains more than 1 metal ion?

It can be hard to detect them all as they can mask each other

Carbonates react with dilute acids to form what?

Carbon dioxide, a salt and water

Most metal carbonates are insoluble, but which 2 aren't?

Potassium carbonate and sodium carbonate

What is a precipitate?

An insoluble solid that come out of a solution

What substance do we add to a solution in metal ion precipitate tests?

Sodium hydroxide

How do we name the precipitate formed in precipitate test?

Name of the metal ion + hydroxide

What colour is the precipitate of aluminium, Al3+?

White- dissolves if more sodium hydroxide is added

What colour is the precipitate of calcium, Ca2+?

White

What colour is the precipitate of magnesium, Mg2+?

White

What colour is the precipitate of copper(II), Cu2+?

Blue

What colour is the precipitate of iron(II), Fe2+?

Green

What colour is the precipitate of iron(III), Fe3+?

Brown

What is the positive result of a sulfate test?

A white precipitate of barium sulfate is formed

How do we carry out the sulfate test?

By adding dilute hydrochloric acid and barium chloride to a solution

What are the halide ions?

Chlroide, bromide and iodide (ions)

What is the test for halides?

Adding silver nitrate in the presence of dilute nitric acid forms a silver halide precipitae

What colour does (silver) chloride go (halide)?

White

What colour does (silver) bromide go (halide)?

Cream

What colour does (silver) iodide go (halide)?

Yellow