Tests For Anions Flashcards
What is testing for Anions
Test for some common negative ions
What are carbonates
Substance that contains CO3*2- ions
How do you detect carbonates
Use a dropping pipette to a add a few drops of dilute acid to a test tube containing the substance
Connect the test tube to a test tube containing lime water
If carbonate ions are present the reaction with the acid will release co2 and turn the lime water cloudy
What do sulfates contain
Sulfate ions SO4*2-
How do you identify sulfate ions
Use a dropping pipette to add a couple drops of dilute hydrochloric acid followed by barium chloride solution to w test tube
A white precipitation will from
Why do you add hydrochloric acid to test for sulfate
To get rid of any traces of carbonate ions before you do the test and not end up with a precipitate
How do you test for halide ions
Add a couple drops of nitric acid and then couple drops of silver nitrate solution
What will Choride, bromide and iodide make if present in solution
Chloride = white precipitate of silver chloride Bromide = cream precipitate of silver bromide Iodine = yellow precipitate of silver iodide
What are cations
Positive ions so metals
How do you test for cations
Flame tests and seeing there colour
What colour will lithium go
Crimson
What colour will sodium go
Yellow
What colour will postassium go
Lilac
What colour will calcium go
Orange red flame
What colour will copper go
Green flame
How do you carry out flame tests
Clean a wire nichrome or platinum wire loop by running with fine emery paper and hold it in the blue flame until it stays a blue flame
Dip the loop into a sample and hold it in the flame
What will metals form when mixed with sodium hydroxide and why is this
Many Metal hydroxide are insoluble and will form a coloured precipitate
What colour will the precipitate of calcium go
White
What colour will the precipitate of copper go
Blue
What colour will the precipitate of iron2 go
Green
What colour will the precipitate of iron3 go
Brown
What colour will the precipitate of aluminium go
White at first
But the redissolves to form a colourless solution
What colour will the precipitate of magnesium go
White
What happens during flame emission spectroscopy
A sample is placed in a flame
The ion heats up and their electrons become excited so they move to higher energy levels
When the electrons drop back to their original energy levels they release energy as light
This light passes through a spectroscope and this can produce a line spectrum of the ion
What does the combination of wavelengths emitted by an ion depend on
Its charge and electron arrangement
Why does each ion produce a different pattern of wavelengths and different like spectrums
Because no two ions have the same charge and same election arrangement
What can the line spectra be used for
To identify ions in solution and calculate their concentrations
What can flame emission spectroscopy be used for and what does this mean
Identify different ions in mixtures and this makes it more useful than flame tests
What are the advantages of using machine
They are very sensitive
Very fast
Very accurate
