Chemistry- chemical analysis.

Flame tests, ion (cations + anions) tests etc.

Li+ flame test

Crimson red

Sodium flame test

Yellow

Potassium flame test

Lilac

Copper flame test

green

Calcium flame test

orange/red

Problems of flame tests

Colours hard to distinguish - low conc

Mixtures of metal ions can mask the colour of the flame

What do flame tests do/ how do they work?

The colors observed during the flame test result from the excitement of the electrons caused by the increased temperature. The electrons "jump" from their ground state to a higher energy level. As they return to their ground state, they emit visible light.

Gas Tests- hydrogen

Squeaky Pop Test.

The presence of hydrogen gas is confirmed by a distinct "squeaky pop" sound when a lit splint is placed in a test tube.

Gas test- Oxygen

Reigniting a glowing splint when placed in test tube confirms the presence of oxygen.

Gas test- Carbon Dioxide

Carbon dioxide is bubbled through the limewater to form a white precipitate.

What is limewater?

Calcium hydroxide dissolved in water.

Gas test- Chlorine

Chlorine gas turns damp litmus paper white and produces a distinct bleach-like smell.

Anion testing- Sulphate

Add dilute hydrochloric acid then barium chloride to the sulphate which should form a white precipitate.

Anion testing- Carbonate

Add acid and we should see effervescence. Carbon dioxide should be given off, but we can test through limewater to prove we started off with carbonate.

Anion tests- Halide tests

Add dilute nitric acid, then dilute silver nitrate to the halide solution, which will produce a colored precipitate depending on the halide present.

Cl- = white precipitate

Br- = cream precipitate

I- = yellow precipitate

Cation tests- Iron II

Add sodium hydroxide (NaOH) which will produce a green precipitate.

Cations test- Iron III

Add sodium hydroxide (NaOH) which will produce a brown precipitate.

Cation tests- Copper II

Add sodium hydroxide (NaOH) which will produce a Blue precipitate

Cation tests- Aluminum

Add sodium hydroxide (NaOH) which will produce a White precipitate.

Add more sodium hydroxide and if it is aluminium it will return back to clear

Cations tests- Calcium

Add sodium hydroxide (NaOH) which will produce a White precipitate.

Cations tests- Magnesium

Add sodium hydroxide (NaOH) which will produce a White precipitate.

What is an element?

Pure substance that cannot be broken down into simpler substances

What is a compound?

when two or more elements are chemically bonded together

What is a mixture?

Two or more elements not chemically bonded together

What is a formulation?

A mixture made for a specific purpose and designed for a useful product

Flame emission spectroscopy

metal ion in solution is placed in a flame

the light is passed through a spectroscope which converts light into a line spectrum, where the positions are specific to a metal ion

Instrumental methods

Method carried out by a machine

Advantages of instrumental methods

Higher sensitivity- work on tiny concentrations

Accuracy-

And rapid