Chemical analysis GCSE

How to test for a carbonate ion?

Add dilute acid, collect the fizzing of gas, bubble the gas through lime water and if it is cloudy it is a carbonate

What is a pure substance?

an element or compound (not mixed with another substance)

How to test the purity of a substance?

melting and boiling point

A pure substance melts at a...

fixed temperature

A fixed substance boils at a...

fixed temperature

What is a Formulation?

A complex mixture that has been designed as a useful product

Examples of formulations

fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods

What type of process is paper chromotography?

physical

What does physical process mean?

No chemicals are used and no new product is formed

What is chromatography used for?

To separate substances in a mixture based on solubility

What is a solvent?

A liquid that will dissolve substances

What is phase is the paper in chromatography? +why?

The stationary phase because it doesn't move

What phase is the solvent in chromatography? +why?

The mobile phase because molecules move

Why does paper chromatography work?

Each chemical in the mixture is attracted to the stationary phase at different extents.

What are the two factors determining how long molecules spend in a phase?

attraction to the paper and solubility

Do strongly attracted chemicals move far?

no

Do weakly attracted chemicals move far?

yes

How many spots will a pure substance form on chromatography paper?

one

Why do we draw the starting line in pencil?

Because if the line was drawn in pen the ink would move up the paper

Rf value equation

Distance travelled by substance / distance travelled by solvent

The Rf value is dependent on the...

solvent used

How to test for hydrgen?

Squeak pop experiment

What is the squeak pop experiement?

add a burning lint to a testube of hydrogen and a pop sound will be heard due to hydrogen buring rapidly

How to test for oxygen?

relight a glowing splint

How to test for carbon dioxide

bubble CO2 in testube of lime water and turns limewater cloudy

What is limewater?

An aqueous solution of calcium hydroxide

How to test for chlorine?

Chlorine Bleaches damp litmus paper

What do flame tests identify?

metal ions

How to set up a flame test

place inoculating loop in chemical and place in a bunsen burner.

What colour flame foes lithium produce?

crimson

What colour flame does sodium produce?

yellow

What colour flame does potassium produce?

lillac

What colour flame does calcium produce?

orange-red

What color flame does copper produce?

green

What are the issues with using flame tests?

The colour can be hard to distinguish (especially at low conc)

A mixture can have multiple ions which masks the colour of the flame

What happens during flame emmision spectroscopy?

Chemical is placed in flame, the light given out is passed into a spectroscope, then is converted into a line spectrum

Can flame emmision spectroscopy tell us the concentration?+why

yes, because the light will be brighter

What is an instrumental method?

A method carried out by a machine

Advantages of using instrumental methods

Very fast, Very accurate and sensitive (only small amount needed)

What happens if you add NaOH (hydroxide) to calcium, aluminium and magnesium solutions?

a white precipitate is formed

Issues with 3 chemicals forming white precipitates

It is difficult to distinguish

If there is an excess of NaOH in Al what does the solution do?

turns colourless

What colour is Copper (11) hydroxide

Blue

What colour is iron (11) hydroxide?

green

what colour is iron (111) hydroxide?

brown

How to test for halide ions?

Add dilute nitric acid and then dilute silver nitrate solution to form different coloured precipitates

What precipitates do chloride ions form?

a white precipitate of silver chloride

what precipitates do bromide ions form?

cream precipitate of silver bromide

What precipitates do iodide ions form?

yellow precipitate of silver iodide

How to test for sulfate ions?

Add dilute HCl and Barium chloride to form a white precipitate