AS Chemistry June exam

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  • Created by: Demelza
  • Created on: 16-05-13 10:46
What is a functional group?
The part of the molecule responsible for its chemical properties
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What is a homologous series
A family of compounds with the same functional group and similar chemical properties. Successive members differs by one carbon atom and two hydrogen atoms.
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What is a nucleophile?
An electron donor.
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What is an electrophile?
An electron acceptor.
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What is a radical?
A species with an unpaired electron.
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What is an addition polymer?
A very long molecular chain, formed by repeated addition reactions of many unsaturated alkene molecules.
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What are the conditions for radical polymerisation?
200 degrees and very high pressures.
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What are the two methods of making ethanol?
Fermentation and Hydration
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What are the reagents and conditions for hydration?
Catalytic hydration of ethene using steam in the presence of a phosphoric acid catalyst. 300 degrees and 60atm.
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What are the reagents and conditions for fermentation?
Glucose, reacted with a yeast catalyst at around 37 degrees.
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What is a primary alcohol?
An alcohol where the carbon that the -OH group is attached to, is only attached to one other carbon atom.
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What is a suitable oxidising agent for the oxidation of primary and secondary alcohols?
Potassium dichromate K2Cr2O7 and Sulfuric acid H2SO4
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What is the product when a primary alcohol is oxidised by heating gently and then distilled immediately?
An aldehyde + water (H2O)
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What is the product when a primary alcohol is oxidised under reflux?
A carboxylic acid + water (H2O)
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What is produced when a secondary alcohol is oxidised?
A ketone
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Can a ketone be oxidised further?
No.
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What is the colour change when an alcohol is oxidised?
Orange to green.
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Can a tertiary alcohol be oxidised? What is the colour change?
No. The colour will remain orange.
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How do you make an ester?
By heating an alcohol with a carboxylic acid in the presence of an acid catalyst.
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What is reflux?
Continuous heating.
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What are some uses of esters?
Esters are used as solvents, adhesives and also as flavourings and perfumes due to their fruity smell.
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What were CFCs originally used for?
Refrigerants, propellants, blowing agents and solvents for the dry-cleaning industry.
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What is the problem with CFCs?
CFCs in the atmosphere cause ozone depletion.
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What are some properties of CFCs?
Non toxic, unreactive, non-flammable.
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What is the equation for percentage yield?
Actual amount (in mol) of product / theoretical amount (in mol) of product x 100
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What is a limiting reagent?
The substance in a chemical reaction that runs out first and 'limits' the reaction.
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What is the equation for atom economy?
molecular mass of desired product / sum of molecular masses of ALL products x 100
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How can particular substances be identified using infrared spectroscopy?
Different types of bonds vibrate at their own frequency allowing you to identify which bonds are present and therefore what the substance is.
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What does the frequency at which a bond vibrates rely on?
Bond strength, bond length and the mass of each atom involved in the bond.
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What is the use of mass spectrometry?
To identify unknown substances and get futher information about their structure and chemical properties.
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What happens during initiation?
Radicals are formed.
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What happens during propagation?
The products of the overall reaction are made.
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What happens during termination?
Any two radicals combine.
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What is enthalpy?
Enthalpy is the heat content that is stored in a chemical system.
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Why do exothermic reactions have a negative enthalpy change value?
Heat has been lost by the chemical system.
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What is an example of an exothermic reaction?
Combustion of fuels.
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Why do endothermic reactions have a positive enthalpy change value?
Heat is gained from the reaction.
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What is an example of an endothermic reaction?
Photosynthesis.
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What is activation energy?
The minimum energy required to start a reaction by the breaking of bonds.
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What are standard conditions?
1atm, 25 degrees C, 1 mol conc.
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What is standard state?
The physical state of a substance under the standard conditions.
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What is the enthalpy change of combustion?
The energy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions.
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What is the enthalpy change of formation?
The enthalpy change that takes place when 1 mol of a compound is formed from its constituent elements in their standard states under standard conditions.
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What is specific heat capacity?
The energy required to raise the temperature of 1g of a substance by 1 degree C.
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What is bond enthalpy?
The enthalpy change that takes place when breaking, by homolytic fission, 1 mol of a given bond in the molecules of gaseous species.
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What is Hess's law?
Hess's law states that: If a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change for each route is the same.
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What is the rate of reaction?
The change in concentration of a reactant or product in a given time.
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What is the catalyst used in the Haber process?
Iron.
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What is the catalyst used in hydrogenation?
Nickel.
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What is a catalyst?
A substance that increasese the rate of a chemical reaction without being used up in the process. A catalyst also provides an alternative route for the reaction by lowering the activation energy.
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What is the Boltzmann distribution?
A graph showing the distribution of energies of molecules at a particular temperature.
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What is dynamic equilibrium?
The equilibrium that exists in a closed system when the rate of the forward and backward reactions is equal.
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What is Le Chatelier's principle?
Le Chatelier's principle states that: when a system in dynamic equilibrium is subjected to change, the position of equilibrium will shift to counteract the change.
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What is an isolated/closed system?
A system where nothing is allowed in or out during the reaction.
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What will happen if the concentration of a reactant is increased during dynamic equilibrium in a closed system.
Equilibrium will shift in the direction which decreases the concentration, i.e. away from the side where the concentration is inreased. if you increase the concentration of a reactant, equilibrium will shift to the right.
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What state must the reactants/products be in, in order to be affected by a pressure change during dynamic equilibrium in a closed system?
Gaseous state.
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What effect does a catalyst have on equilibrium?
A catalyst will increase the rate of the forward and reverse reactions equally but does NOT alter the position of equilibrium. A catalyst increases the rate at which equilibrium is established.
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Name two chemical processes that exist in equilibrium systems.
The Haber process and the Contact process.
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What is the greenhouse effect?
The greenhouse effect is a natural process which keeps the temperature of our planet stable.
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What is the problem with an increase in the greenhouse gases?
An increase in greenhouse gases will cause the greenhouse effect to become more severe, leading to global warming.
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Name three greenhouse gases.
Water vapour, CO2, methane.
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Name three ways in which CO2 is produced.
Volcanic eruptions, respiration of animals and the decay of organic matter (such as plants).
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What is GWP?
Global Warming Potential - the ability of a trace gas to cause global warming.
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How do gases absorb radiation?
Infrared radiation causes the bonds to vibrate which gives out a form of radiation which is then absorbed by another bond in another molecule.
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Name 4 alternative energy resources.
Wind turbines, tidal power, solar panels and nuclear plants.
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What is CCS?
Carbon Capture and Storage - a way of capturing CO2 from power stations and storing it away safely instead of allowing it to be released into the atmosphere.
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Name two ways of capturing carbon.
Porous rocks. Extracting the final 30% of oil from used oilfields. Mineral storage.
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In which layer of the atmosphere is ozone good?
Stratosphere.
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In which layer of the atmosphere is ozone bad?
Troposphere.
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Why is ozone in the troposphere bad?
Has harmful effects, is toxic, causes respiratory problems.
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Which wavelengths does ozone block completely?
Shorter wavelengths below 320nm. UVc radiation.
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What are some potential dangers of UVa and UVb radiation?
UVa radiation is not very damaging but UVb can cause sunburn, skin cancer and sometimes genetic damage.
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How is ozone formed?
O2 absorbs UV radiation and forms 2O atoms which then react with O2 to form ozone which is O3.
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What can cause ozone depletion?
O atoms in the atmosphere, also radicals which break the O3 down into O2 plus an oxygen compound.
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Name three pollutants.
Carbon monoxide, nitrogen oxides and unburnt hydrocarbons.
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Name some uses of carbon dioxide.
Expanding foam, as a solvent, decaffeinated coffee, for beer, for dry cleaning etc.
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What is adsorption?
The process that occurs when a gas, liquid or solute is held to the surface of a solid or, more rarely, a liquid.
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Other cards in this set

Card 2

Front

What is a homologous series

Back

A family of compounds with the same functional group and similar chemical properties. Successive members differs by one carbon atom and two hydrogen atoms.

Card 3

Front

What is a nucleophile?

Back

Preview of the front of card 3

Card 4

Front

What is an electrophile?

Back

Preview of the front of card 4

Card 5

Front

What is a radical?

Back

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