Summer Assessment 3- more Flashcards
how can you work out the speed of a reaction on a graph
- by recording the amount of product formed or the amount of reactant used up over time
- the steeper the line on a graph the fatser the reaction
- line becomes less steep as reactants are used up
what do the quickest reactions show on a graph
-they have the steepest line and become flat in the least time
what does the rate of a chemical reaction depend on
- collision frequency of reacting particles- the more collisions the faster the reaction
- energy transferred during a collision
what is activation energy
-the minimum amount of energy particles need to react
why to particles need activation energy
-to break the bonds in reactants to start to the reaction
explain the method you would carry out to measure how surface area affects rate
- use marble chips and HCL
- set up the apparatus so you have a conical flask with marble chips in it as well as HCL- attach to the bung in the conical flask a gas syringe
- measure volume of gas produced using a gas syringe
- take readings at regular intervals and record the results
why does using finer particles of solid mean a higher rate of reaction
-as finer particles mean the marble has a larger surface area
what effect does changing the concentration of acid have on the rate of reaction
a higher concentration gives a faster reaction
what is the general formula for alkenes
CnH2n
what is the empirical formula (for ethene)
CH2
-simplest ratio of atoms
what is the molecular formula (for ethene)
C2H4
-actual number of atoms of each element in a molecule
what is the structural formula (for ethene)
CH2CH2
-shows arrangement of atoms carbon by carbon
what is a homologous series
-a group of compounds that can all be represented by the same general formula
what is a functional group
- a group of atoms that determine how a compound typically reacts
definition of isomer
two or more molecules with the same molecular formulae but different structural formula
what can you infer from differently shaped carbon chains
- these isomers have similar chemical properties
- but different physical properties due to the change in shape of the molecules
what could you infer from functional groups being in different places
-these isomers have different physical properties
what could you infer from functional groups being different
-these isomers have different physical and chemical properties
What is a hydrocarbon?
a compound of hydrogen and carbon only
What happens when you burn a fuel?
releases energy in form of heat
What is burning a fuel also known as?
-combustion reaction
Why do hydrocarbons make great fuels?
as the combustion reaction that happens when you burn them in oxygen gives out lots of energy
hydrocarbon + oxygen =
carbon dioxide + water
What is complete combustion
-when you burn hydrocarbons in plenty of oxygen, the only products are CO2 and water
What type of reaction is hydrogen + oxygen?
complete combustion
What does incomplete combustion produce?
carbon monoxide + soot + carbon
When does incomplete combustion occur?
when there is not enough oxygen around
How is carbon monoxide is poisonous?
- It combines to red blood cells and stops blood doing proper job of carrying oxygen round the body
- lack of oxygen in blood supply can result in death
What is acid rain caused by?
- sulfur dioxide
- nitrogen oxides
When may sulfur dioxide and nitrogen oxides be produced?
when fractions from crude oils are burned
Where does sulfur dioxide come from?
comes from sulfur impurities in hydrocarbon fuel
How are nitrogen oxides formed?
- when temp is high enough for nitrogen and oxygen react in the air
- this often happens in car engines
What is made when sulfur dioxide and nitrogen oxides mix with water vapour in the clouds?
- dilute sulfuric acid and nitric acid
- the rain that then falls from these clouds is known as acid rain
Why is acid rain an issue?
- causes lakes to become acidic
- many plants and animals die as a result
What are alkanes?
- saturated hydrocarbons
- they are chains of carbon atoms surrounded by hydrogen atoms
- single bonds between carbon atoms
What is the general formula for alkanes?
CnH2n+2
What are the names of the first five alkanes?
methane ethane propane butane pentane
What do alkanes burn in?
complete combustion reactions
Write the word equation for the burning of propane
propane + oxygen -> carbon dioxide + water
What do alkanes react with and what is this called?
alkanes react with halogens to form haloalkanes
What type of light is needed to make a haloalkane?
ultraviolet light
What type of reaction is a haloalkane made in?
substitution reaction
What is a substitution reaction?
hydrogen atom from alkane is substituted with chlorine or bromine
Write the word equation for the reaction of bromine with an alkane (methane)
methane + bromine -> bromomethane + hydrogen bromide
What are addition polymers made from?
-unsaturated monomers
How is an addition polymer formed?
by joining up many small molecules called
monomers
What are polymers?
A large molecule made when many small molecules (monomers) join together. Consists of many repeat units.
What is addition polymerisation
When lots of unsaturated monomer molecules open up their carbon-carbon double bonds and join together to form polymer chains
What are Monomers?
Molecules which can join up to form a polymer.
What does ethene become in addition polymerisation?
-how does its displayed formula change
poly(ethene)- (c2H4)n
ethene displayed formula: H H \ / C = C / \ H H
—> pressure and a catalyst
H H H H H H
-C-C-C-C-C-C-
H H H H H H
poly(ethene)
What does propene become in addition polymerisation?
-how does its displayed formula change
poly(propene)- (C3H6)n
propene displayed formula: H H \ / C = C / \ H CH3
—> pressure and a catalyst
H H
(-C-C-) n
H CH3
poly(propene)
Why is it diffiuclt to get rid of addition polymers
- as most addition polymers are inert - they don’t react easily
- as the carbon-carbon bonds in the polymer are very strong and aren’t easily broken
- this means it takes a v long time for addition polymers to biodegrade
- the burning of plastics also release toxic gases, so you can’t get rid of addition polymers that way
Name 2 ways why polymers are hard to get rid of
- it takes a long time for addition polymers to biodegrade
- you can’t burn them either as that releases toxic gases
What is condensation polymerisation
Polymerisation of monomers in which each time two monomers combine, a small molecule such as water or hydrogen chloride is removed (e.g. a dicarboxylic acid and a diol).
