Separate Chemistry 2

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Pass the biscuits

Cards (85)

Why must a test for a specific ion be unique?
To give an easily observable result specific to the present ion.
How would you carry out a flame test for ions?
Clean a nichrome wire using hydrochloric acid, turn the Bunsen burner onto the blue flame, dip the wire in a solution if the substance being tested, place the wire in the flame and record the colour.
Lithium ion flame.
Red
Sodium ion flame.
Yellow
Potassium ion flame.
Lilac
Calcium ion flame.
Orange-red
Copper ion flame.
Blue-green
Why must the wire be cleaned before carrying out a flame test?
To removed any unwanted ions that might obscure the colour of the flame.
Why can a flame test not be used for a mixture of ions?
The flames will merge so individual ions can’t be identified.
What is a precipitate?
An insoluble solid suspended in a liquid.
How can you test for aqueous metal ions?
Add sodium hydroxide solution to the metal ions, observe the colour of the precipitate.
Sodium hydroxide with calcium ions.
White precipitate.
Sodium hydroxide with copper (II) ions.
Blue precipitate.
Sodium hydroxide with iron (II) ions.
Green precipitate.
Sodium hydroxide with iron (III) ions.
Brown precipitate.
Sodium hydroxide with aluminium ions.
White initially but excess NaOH re-dissolves to form a colourless solution.
Sodium hydroxide with ammonium ions.
A pungent smelling gas is produced (NH3) which will turn damp red litmus paper blue.
How could you distinguish between two solutions containing aluminium ions and calcium ions?
Add sodium hydroxide solution: white precipitate for calcium ions, colorless for aluminium ions.
How can you test for carbonate ions?
Add a few drops of HCl to the sample in the test tube, connect this to another test tube of limewater. If carbonate ions are present, they will react with the acid to produce carbon dioxide which will turn the limewater cloudy when bubbled through it.
Reaction between hydrochloric acid and sodium carbonate. 
Na2C03 + 2HCl - CO2 + 2NaCl + H2O
How can you test for sulfate ions?
Add HCl to remove any CO32- ions as these will obscure the results, add a couple drops of barium chloride. If sulfate ions are present a white precipitate of barium sulfate will form.
Reaction between barium chloride and magnesium sulfate.
BaCl2 + MgSO4 - BaSO4 + MgCl2
BaSO4 is a white precipitate.
Test for halide ions.
Add a few drops of nitric acid to react with any carbonate ions which might obscure the result, add a couple drops of silver nitrate. Observe the colour of precipitate.
Precipitate of silver nitrate and chloride solution.
White precipitate of silver chloride.
Precipitate of silver nitrate added to bromide solution.
Cream precipitate of silver bromide.
Precipitate of silver nitrate and an iodide solution.
Yellow precipitate of silver iodide.
What is meant by instrumental methods of analysis?
Methods of analysis that use machinery such as mass spectrometry and gas chromatography.
Benefits of using instrumental methods for analysis.
Accurate, sensitive, quick to carry out.
What is a flame photometer?
A device in inorganic analysis used to measure the concentration of metal ions.
How can a flame photometry be used to identify metal ions?
An emission spectrum is produced an each ions produced a unique spectrum so comparing the unknown spectrum to reference spectra can identify the ion.
How can a flame photometry be used to determine the concentration of metal ions?
Take readings using a flame photometer of the metal ions at different concentrations, plot a calibration curve, take a reading of the unknown sample and compare to the curve.
Major advantage of using flame photometry compared to simple flame testing?
Flame photometry can be used to analyse a mixture of ions whereas flame tests can only be used to identify one ion at a time.
General formula for alkanes? 
C n H 2n+2
First four alkanes.
Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10
What bonds are formed in alkanes between the carbon and hydrogen atoms?
Covalent bonds.
General formula for alkenes. 
C n H 2n
First four alkenes.
Ethene - C2H4
Propene - C3H6
Butene - C4H8
Pentene - C5H10
What is a functional group?
A group of atoms responsible for the main chemical properties of a compound.
Functional group in alkenes.
C=C double bond.
Difference between but-1-ene and but-2-end.
Both alkenes with 4 carbons but the C=C bond is found between different carbons in the chain, 1 has it between the first and second and 2 has it between the second and third carbon in the chain.