What are the products of reactions of hydrocarbons and how do they react? Flashcards
Why are alkanes good fuels?
they are fairly stable but still burn readily in an exothermic reaction.
what common fuels contain mixtures of alkanes and other hydrocarbon molecules ?
petrol, diesel and kerosene
what is the main component of natural gas?
methane- the simplest alkane
what are the products of burning hydrocarbon fuels in excess oxygen?
carbon dioxide and water vapour
what happens in a substitution reaction?
when an atom or functional group in a molecule is replaced or substituted by another
how must a reaction vessel at room temp and in the dark, containing a mixture of an alkane and chlorine gas react?
the reaction must be initiated by ultraviolet light (UV)
write out the reaction between methane and chlorine
(reference pg 312)
for each molecule of chlorine gas (Cl2) that reacts……
a hydrogen atom on the alkane is replaced by a chlorine atom.
why are alkenes more reactive than alkanes?
because they are unsaturated and they have a double bond.
what affect does the double carbon-carbon covalent bond in alkenes have on its chemical properties?
alkenes will generally react more readily and with more chemicals than alkanes.
what happens in an addition reaction?
the addition of a small molecule to the double bond of the alkene
what changes are made to the alkene in an addition reaction?
two products are formed into one, the double bond becomes single, the unsaturated compound because saturated and the atoms of the small molecule are added across the double bond.
write out the reaction between ethene and hydrogen bromide. what is the product?
(reference pg 313) the only product is bromoethane
what four different types of addition reactions do alkenes undergo?
reaction with: hydrogen, halogens, hydrogen halides and water
how do alkenes and hydrogen gas react?
in the presence of a metal catalyst: nickel
what is the reaction of an alkene and hydrogen gas called ?
hydrogenation reaction
write out the hydrogenation of ethene with hydrogen gas
reference pg 313
write out the addition reaction of ethene and bromine
reference pg 314
how do the reactions of alkenes and halogens occur?
at room temperature without a catalyst
why is bromine often used as a test for the presence of a carbon-carbon double bond?
because of the ease and speed with which it reacts with an alkene
what happens when an alkene is added to aqueous bromine?
the alkene reacts with the coloured bromine and the solution loses colour
what happens when an alkane is added to aqueous bromine?
no addition reaction occurs so there is no colour change
what are hydrogen halides?
chemical molecules that contain one hydrogen atom and one halogen atom.
write out the reaction between the alkene but-2-ene and the hydrogen halide, hydrogen chloride
reference pg 314
write out what happens when you react hydrogen chloride and but-1-ene
reference pg 314- two isomers are possible as products
what happens in a reaction of an alkene and water?
under specific conditions, alcohol is produced
what is the molecular formula for sulphuric acid?
H2SO4
what is the molecular formula for phosphoric acid?
H3PO4
write out the reaction of ethene and water using a catalyst to increase rate of reaction to produce ethanol
the addition reaction of steam and ethene using a sulphuric acid or phosphoric acid catalyst.
what is a hydration reaction?
reactions that involve water as a reactant
why is the reaction of ethene and steam to produce ethanol used for commercial manufacture ?
because it is a one-step process that uses little energy and the heterogeneous nature of the reaction system means it is easy to remove the product from the reaction mixture.
write out the reaction of propene with water in the presence of dilute sulphuric acid
two isomers are possible products: propan-1-ol and propane-2-ol
what is needed for the reaction between alkenes and water?
the presence of a high amount of acid with catalytic effect
why is ethene such an important chemical?
since it is an alkene, it undergoes addition reactions that convert alkenes into a number of substances. ethene is so useful because it can be used as a starting material (feedstock) from which other substances can be made.
what are the 3 steps in a hydrogenation reaction?
- hydrogen molecule react with the metal catalyst, forming two weak metal-hydrogen bonds.
- alkene molecule reacts with the metal catalyst and the double bond breaks into a weak metal-hydrogen bond
- the metal catalyst causes the hydrogen atoms to join to the carbon atoms, creating the final molecule.
why is there no catalyst needed in a hydrogen halide addition reaction?
no catalyst is needed due to the reactivity of halogens.
what is the reaction between water and an alkene, and what is its catalyst?
water is added across the double bond using dilute H2SO4 as a catalyst, where the alkene becomes and alcohol. (hydrogenation)
what os the reaction between water and an alkyne, and what is its catalyst?
water is added across the triple bond using mercury (II) compounds and sulphuric acid. the addition of water will produce a ketone. (except for ethyne)
