Separate Chemistry 1 Flashcards
Why must a test for a specific ion be unique?
Texts are used to identify ions and must be unique so that the test gives an easily observed result which is specific to the ion that is present
How would you carry out the flame test to test for ions?
Clean a micrometer wire using hydrochloric acid, turn the Bunsen burner onto the blue flame, dip the wire in a solution of the substance being tested and place the wire in the flame and record the colour
What is the result of the flame test on lithium ions?
Crimson flame
What is the result of the flame test on sodium ions?
Yellow flame
What is the result of the flame test on potassium ions?
Lilac flame
What is the result of the flame test on calcium ions?
Orange-red flame
What is the result of the flame test on copper ions?
Blue-green flame
Why must the wire be cleaned before carrying out a flame test?
To remove any unwanted ions that might obscure the colour of the flame
Why can a flame test not be used when a compound contains a mixture of metal ions?
The flame colours of the ions will blend together so the individual flame colours won’t be seen meaning the ions can’t be identified
What is a precipitate?
An insoluble solid suspense in a liquid
Without using the flame test, how can you test for aqueous metal ions?
Add sodium hydroxide solution to the metal ions, observe the colour of the precipitate
What colour precipitate forms when sodium hydroxide reacts with calcium ions?
White
What colour precipitate forms when sodium hydroxide reacts with copper(II) ions?
Blue
What colour precipitate forms when sodium hydroxide reacts with iron(II) ions?
Green
What colour precipitate forms when sodium hydroxide reacts with iron(III) ions?
Brown
What colour precipitate forms when sodium hydroxide reacts with aluminium ions?
White
What is observed when sodium hydroxide reacts with ammonium ions?
A pungent smelling gas is produced which will turn damp red litmus paper blue
How could you distinguish between two solution containing aluminium ions and calcium ions?
Add excess sodium hydroxide, both will form white precipitates initially, the precipitate formed from aluminium ions will re-dissolve to form a colourless solution
How can you test for carbonate ions?
Add a few drops of HCI to the sample in a test tube, connect this test tube to a test tube of limewater, if carbonate ions are present, they will react with the acid to produce carbon dioxide which will turn the limewater cloudly when it’s bubbled through limewater
How can you test for sulfate ions?
Add HCI to remove any CO3 2- ions as these will obscure the results, add a couple of drops a barium chloride and if sulfate ions are present a white precipitate of barium sulfate will form
How do you carry out a rest for halide ions?
Add a few drops of nitric acid to react with any carbonate ions which might obscure the results, add a couple of drops of silver nitrate and observe the colour of the precipitate
What colour precipitate is formed, when silver nitrate is added to a chloride solution?
White precipitate of silver chloride
What colour precipitate is formed, when silver nitrate is added to a bromide solution?
Cream precipitate of silver bromide
What colour precipitate is formed, when silver nitrate is added to a iodide solution?
Yellow precipitate of silver iodide
What is meant by the phrase instrumental methods of analysis?
Methods of analysis that use machinery such as gas chromatography
What are the benefits of using instrumental methods for analysis?
Accurate, sensitive and quick to carry out
What is a flame photometer?
A device used in inorganic analysis, it can be used to identify or determine the concentration of metal ions
How can a flame photometry be used to identify metal ions?
An emission spectrum is produced by the flame photometer, each metal ion produces an unique spectrum so comparing the unknown spectrum to reference spectra can identify the ion
How can a flame photometry be used used to determine the concentration of metal ions?
Take reading using a flame photometer of the metal ions at different concentrations, plot a calibration curve and take a reading of the unknown sample and compare to the curve e
What is the major advantage of 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
What is the general formula for alkanes?
C(n)H(2n+2)
What was the name of the first four alkanes?
Methane (CH4), Ethane (C2H6), Propane (C3H8) and Butane (C4H10)
What type of bond are formed between carbon and hydrogen atoms in alkanes?
Covalent bonds
Why are alkanes saturated hydrocarbons?
All C-C bonds are single bonds and only contain carbon and hydrogen atoms
What is the general formula for alkenes?
C(n)H(2n)
What are the names of the first four alkenes?
Ethene (C2H4), Propene (C3H6), Butene (C4H8) and Pentene (C5H10)
Why are alkenes unsaturated hydrocarbons?
They are compounds made up of only carbon and hydrogen atoms and they contain double carbon bonds
What is a functional group?
The group of atoms responsible for the main chemical properties of a compound
What functional group do alkenes contain?
C=C double bond
What is the difference between but-1-ene and but-2-ene?
But-1-ene and but-2-ene are both alkenes with 4 carbons but the C=C bind is found between different carbons in the chain. In but-1-ene, the double bond is between the first and second carbon whereas in but-2-ene, it’s between the second and third carbon in the chain
How can bromine water be used to distinguish between alkanes and alkenes?
When bromine water is added to an alkane, the solution remains orange, when bromine water is added to an alkene,the solution changes from orange to colourless
Why do alkenes decolourise bromine water?
Alkenes are unsaturated, the double bond allows alkenes to react with bromine to form a bromoalkane
What is produced when a hydrocarbon is completely combusted?
Water and carbon dioxide are produced, carbon and hydrogen are oxidised
What is the balanced equation for the combustion of propane?
C3H8 + 5O2 -> 3CO2 + 4H2O
What type of reactions happens when energy is released when hydrocarbons undergo complete combustion?
Exothermic reaction
What is a polymer?
A substance of high average relative molecular Nass made up of small repeating units
How are polymers made?
By linking together lots of small molecules to form a long chain
What is the name of the process in which ethene molecules join together to form a polymer?
Addition polymerisation
How can ethene molecules undergo polymerisation to form the polymer poly(ethene)?
One of bonds in each C=C double bond breaks and forms a bond with an adjacent monomer, forming a long chain polymer and this requires many ethene monomers
What is the name of the product formed from the addition polymerisation of ethene?
Poly(ethene)
Can chloroethene undergo addition polymerisation?
Yes because it contains a C=C double bond, the product is poly(chloroethene) or PVC
What properties of poly(propene) makes it suitable for making buckets and crates?
Flexible and strong
Poly(ethene) is commonly used to make plastic bags, bottles and coatings of electrical wires, why?
Inexpensive, electrical insulator and flexible
What is a common use of poly(chloroethene)?
Use for window frame because it’s tough, cheap and long product life
What is a common use of poly(tetrafluoroethene) PTFE?
Coating for non-stick pans because it’s tough and non-stick
By what process are polyesters formed?
Condensation polymerisation
Why are polyesters condensation polymers?
Because a small molecule is released when the bond is formed between two monomers