Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
55 Cards in this Set
- Front
- Back
|
What is the volume of one mole of any gaseous substance at standard temperature and pressure.
|
24dm
|
|
|
Define standard enthalpy change of combustion.
|
The amount of energy released when one mole of fuel is completely combusted.
|
|
|
What is an exothermic reaction?
|
A reaction that GIVES OUT energy to the environment. Enthalpy change of an exothermic is always negative.
|
|
|
What is an endothermic reaction?
|
A reaction that TAKES IN energy from the surroundings. Enthalpy change of an endothermic reaction is always positive.
|
|
|
Define standard enthalpy change of formation.
|
The enthalpy change when one mole of a substance is formed from its constituent elements in their standard state. This can be positive or negative.
|
|
|
What is entropy.
|
Entropy is the number of ways in which particles can be arranged.
|
|
|
What causes an increase in entropy.
|
Change in state from
solid-->lquid-->gas. Mixtures and solutions have greater entropy than unmixed constituents. An increase in the number of particles. |
|
|
What is Hess's law?
|
This states that as long as the strating and finishing points of a reaction are the same, the enthalpy change will be always be the same regardless of how you get from start to finish.
|
|
|
What are enthalpy cycles?
|
Enthalpy cycles use Hess's law and often the enthalpy change of formation to determine the enthalpy change of a reaction.
|
|
|
What is bond enthalpy?
|
The average energy required to break the bonds in one mole of gaseous compounds.
|
|
|
With regards to bond enthalpy, what is bond breaking?
|
Bond breaking is always endothermic.
|
|
|
With regards to bond enthalpy, what is bond making?
|
Bond making is always exothermic.
|
|
|
What determines the strength of a bond?
|
A high bond enthalpy means a high bond strength. The shorter a bond the stronger the bond. Double bonds are stronger than single bonds.
|
|
|
What is functional group in an alcohol?
|
A hydroxyl group R-OH
|
|
|
Should I be able to name alcohols?
|
Yes - go and look it up in your revision guide!
|
|
|
What products do alcohols give when they completely combust?
|
Carbon dioxide and water.
|
|
|
What functional group do ethers have?
|
An alkoxy group -OR.
|
|
|
What are oxygenates?
|
Oxygen bearing chemicals that can be added to fuels to increase efficiency, reducing incomplete combustion.
|
|
|
Give two example of oxygenates.
|
Alcohols and ethers.
|
|
|
What is the general formula for alkanes?
|
C(n)H(2n+2)
|
|
|
What are the structural properties of alkanes?
|
They are saturated (all the carbon bonds have single bonds between them).
They are aliphatic (don't contain a benzene ring). |
|
|
What are the products of complete combustion of alkanes?
|
Carbon dioxide and water.
|
|
|
Do I need to know how to name them?
|
Yes, so go and learn how.
|
|
|
What structure and bond angles do alkanes have?
|
They are all tetrahedral and have bond angles of 109 degrees.
|
|
|
What is the general formula of a cycloalkane?
|
C(n)H(2n)
|
|
|
What are the structural properties of cycloalkanes?
|
They are saturated and aliphatic (don't contain a benzene ring).
|
|
|
What is the general formula for alkenes?
|
C(n)H(2n)
|
|
|
What are the structural properties of alkenes?
|
They are unsaturated (have a double bond between some of the carbons) and aliphatic (no benzene ring).
|
|
|
What are the structural properties of arenes?
|
They are unsatuated and aromatic (contain a benzene ring).
|
|
|
What is a structural isomer?
|
A molecule that has the same molecular formula, but a different structural formula.(ie the atoms are arranged in a different order).
|
|
|
What are the three ways of creating a structural isomer?
|
1. Differnt carbon chains (ie adding branches).
2. Different position of the functional group. 3. Different functional groups. |
|
|
What is structural isomerism used for?
|
To increase the octane number of fuels and prevent auto ignition.
|
|
|
What does the octane number represent?
|
The tendency of a fuel to auto-ignite.
|
|
|
What does a high octane number mean?
|
A low tendency to auto-ignite.
|
|
|
What problems does auto-ignition cause?
|
Knocking, reducing performance and damaging engines.
|
|
|
What increases octane number?
|
Branched alkanes; shorter chain alkanes; making cycloalkanes-->arenes; use of oxygenates.
|
|
|
What is a catalyst?
|
A catalyst is a substance that acts to alter the rate of reaction but is not permanently altered by the reaction.
|
|
|
What is a heterogeneous catalyst?
|
A catalyst in a different physical state to the reactants.
|
|
|
What is cracking?
|
The breaking down of long chain alkanes into shorter ones and alkenes, in order to increase the octane number.
|
|
|
What is reforming?
|
Alkane-->cycloalkane + hydrogen.
Cycloalkane-->arenes + hydrogen. In terms of octane number: arenes > cycloalkanes > alkanes |
|
|
What are the 5 main pollutants from a car engine?
|
1. Unburnt hydrocarbons.
2. CO 3. CO2 4. NO(x) 5. SO(x) |
|
|
Where do the unburnt hydrocarbons come from?
|
Incomplete combustion of the fuel, some hyrdocarbons are unburnt.
|
|
|
What is the effect of unburnt hydrocarbons?
|
Contribute to the formation of photochemical smog, causing respiratory problems.
|
|
|
Where does the CO come from?
|
Incomplete combustion of the fuel.
|
|
|
What are the effects of CO?
|
Harmful to humans.
|
|
|
Where does the CO2 come from?
|
The complete combustion of the fuel.
|
|
|
What are the effects of CO2?
|
Causes the greenhouse effect and global warming.
|
|
|
Where do the NO(x) come from?
|
Nitrogen from the air reacts with oxygen in the air at the high temperatures in the engine.
|
|
|
What are the problems of NO(x)?
|
Contributes to the formation of photochemical smog. Causes acid rain.
|
|
|
Where do the SO(x) come from?
|
Sulphur impurities in the petrol react with oxygen in the air.
|
|
|
What are the problems of SO(x)?
|
Causes acid rain.
|
|
|
What is energy density?
|
=enthalpy change of combustion * number of moles in 1kg of the fuel. Measured in kJ/kg
|
|
|
What properties should a good fuel have?
|
High energy density.
High octane number. Produce few pollutants. Suitable boiling point. |
|
|
What about hydrogen as a fuel?
|
Good - high energy density, and only produces water.
Bad - Unsuitable boiling point (too low) |
|
|
What about ethanol as a fuel?
|
Good - renewable, high octane number, oxygenate->less pollutants.
|
