Hydrocarbons (Separate chemistry 2) Flashcards
Silver nitrate solution is used to test for the presence of chloride ions. A white precipitate of silver chloride forms:
Ag[+] + Cl[-] -> AgCl
(aq) (aq) (s)
Carbonate ions also form a precipitate:
2Ag[+] + CO[3][2-] -> Ag[2][CO[3]
Explain why, when carrying out a test for chloride ions, dilute nitric acid is added to the sample before adding silver nitrate solution. [2]
the nitric acid reacts with the carbonate ions
as the sample no longer contains carbonate ions, they cannot form a precipitate, which gives a false-positive result
Explain how you could carry out a test to distinguish between sodium chloride solution and sodium iodide solution [3]
add dilute nitric acid to react with carbonate ions/ions that would interfere with the test, then add silver nitrate solution
sodium chloride solution produces a white precipitate of silver chloride, sodium iodide solution produces a yellow precipitate of silver iodide
Write a balanced equation for the complete combustion of butane [2]
2C[4]H[10] + 13O[2] -> 4CO[2] + 5H[2]O
Hexane is an alkane with six carbon atoms.
a) give the molecular formula of hexane, and draw its structure [2]
b) Explain why hexane is ‘saturated’ [1]
c) write a balanced equation for the complete combustion of hexane [2]
a) C[6]H[14]
b) 6 carbons surrounded by 14 total hydrogens
c) it has only C-C bonds/no C=C bonds/no double bonds
d) 2C[6]H[14] + 19O[2] -> 12CO[2] + 14H[2]O
a) Write the molecular formula of butene. [1]
b) The functional group in a butene molecule can be in two different places. Draw the structures of the two forms of butene, showing all their covalent bonds. [2]
a) C[4]H[8]
b) two isomers
bond inbetween 1st and 2nd
inbetween 2nd and 3rd
Hexane, C[6]H[14], and hexene, C[6]H[12]. are both liquids at room temperature.
a) Explain why hexene is described as an unsaturated hydrocarbon. [3]
b) Describe a chemical test to distinguish between hexane and hexene. [3]
a) hexene molecules contain carbon and hydrogen only, and the functional group C=C (contains double bonds)
b) add bromine water
there is no change with hexane
bromine water is decolourised with hexene
(clear doesn’t mean colourless)
Complete the questions for both addition and condensation polymerisation: [2]
- number of different molecules
- number of different products
- addition: one
- condensation: two
- addition: one
- condensation: two
PET is a polyester used to make drinks bottles and fleece linings.
a) State whether PET is an addition polymer or a condensation polymer. [1]
b) State the type of monomers needed to manufacture PET [2]
c) Name the product formed, other than PET, during the manufacture of PET [1]
a) condensation polymer
b) -molecules with two carboxylic acid groups
- molecules with two alcohol groups
c) water
Starch is a substance found in plant cells.
Describe the structure of starch. [2]
starch is a polymer made from many sugar monomers joined together
Give two advantages and two disadvantages of the disposal of polymers by recycling rather than by landfill. [4]
Dumping polymers in landfill sites is a waste of a non-renewable resource, as polymers are made from crude oil
recycling means that less waste goes into landfill, on the other hand, recycling is expensive because the different polymers must be collected and sorted
some polymers cannot be recycled
Describe the advantages and disadvantages of disposing of waste polymers by:
a) combustion [2]
b) burying them in landfill sites [2]
a) does not use up landfill sites, useful energy can be obtained
- release of polluting gases, waste of finite resources
b) does not release polluting gases, does not need complex equipment
- running out of landfill sites, sites take up space, waste does not degrade quickly
State two ways in which waste polymers may be made into new objects. [2]
melting and reforming into new objects
breaking down into new raw materials
Suggest reasons that explain why it has become worthwhile for companies in China to pay for waste poly(ethene) to be shipped to them from America and Europe. [2]
poly(ethene) is made from crude oil
the cost of crude oil may be higher than the cost of recycling
