Developing Fuels(DF) Flashcards
What is an exothermic reaction?
A reaction that releases energy/heat to the surroundings, causing the temperature of the surroundings to increase
In an exothermic reaction does the products or reactants have more energy?
Reactants
What happens to the difference in energy between reactants and products in an exothermic reaction?
The difference is release to the surroundings
What is an endothermic reaction?
A reaction that takes in heat/energy from the surroundings, causing the temperature of the surroundings to decrease
In an endothermic reaction does the products or reactants have more energy?
Products
What is activation energy?
The miniumum amount of energy that particles must have to react
What is a catalyst?
A catalyst is something which increases the rate of reaction, by providing an alternative pathway for the reaction with a lower activation energy, without being used up
Why are catalysts not involved in the chemical equation for a reaction?
They are not used up during the reaction
What are the benefits of using a catalyst?
-Allows a reaction to happen at a lower temperature=saves energy
-Saves money
What is enthalpy ΔH ?
The measure of heat energy in a system
How can you calculate enthalpy change?
ΔH =H products- H reactants
What is enthalpy change measure in?
kJ mol-1
For an exothermic reaction will the enthalpy change be positive or negative?
Negative
For an endothermic reaction will the enthalpy change be positive or negative?
Positive
What is the equation that links energy released, mass, specific heat capacity and temperature change?
Q = mc∆T
Does breaking bonds release or take in energy?
Takes in energy
Does making bonds release or take in energy?
Releases energy
What happens as bond length decreases?
The bond becomes stronger
Why might calculated bond energy value differ from the figure provided?
-Bond energies are average values from several compounds=not always precise
-Bond energies assume all molecules are in a gaseous state
If the energy needed to break the bonds is greater than the energy released when the new bonds are made is the reaction endo or exothermic?
Endothermic
If the energy needed to break the bonds is less than the energy released when new bonds are made the reaction is the reaction endo or exothermic?
Exothermic
Describe how to calcuale the enthalpy change of solution?
- Place known volume of water into a polystyrene beaker
2.Add known mass of the other compund to the water and stir
3.Measure temperature of water before and after
Can atoms rotate freely around a single or double bond?
Single bond, in a double bond there is restricted rotation
What are stereoisomers?
Molecules with the same structural formula but the atoms have a different spacial arrangment
