developing fuels (DF) Flashcards
What is the ideal gas equation?
pV = nRT
What is enthalpy change?
Heat energy transferred in a reaction at constant pressure.
What is an exothermic reaction?
A reaction that gives out energy, resulting in a temperature increase.
What is an endothermic reaction?
A reaction that absorbs energy, resulting in a temperature decrease.
How do you calculate enthalpy change from bond enthalpies?
Energy absorbed when bonds are broken - energy released when bonds are made.
What are average bond enthalpies?
Energy needed to break one mole of bonds in the gas phase, averaged over many compounds.
What is bond enthalpy related to?
The distance between two nuclei where repulsive and attractive forces balance.
How does bond enthalpy relate to attraction and bond length?
Stronger attraction = higher bond enthalpy and shorter bond length.
What is Hess’s Law?
The total enthalpy change is always the same regardless of the route taken.
What do enthalpy level diagrams show about stability?
Substances with lower enthalpy are more stable.
Why are intermediates usually short-lived?
They have very high enthalpy and quickly convert into products.
What is the standard enthalpy change of neutralisation?
The enthalpy change when an acid and alkali react under standard conditions to form one mole of water.
What is the formula for calculating enthalpy change?
q = m × c × ΔT
What do the variables in q = mcΔT represent?
q = heat energy (J), m = mass of solution (g), c = 4.18 J/g/K, ΔT = temperature change (K).
What is a catalyst?
A substance that increases the rate of reaction by lowering the activation energy and remains chemically unchanged.
What is a heterogeneous catalyst?
A catalyst in a different state to the reactants.
How do heterogeneous catalysts work?
Via adsorption (bond breaking), radical formation, bond formation, and desorption.
What is catalyst poisoning?
When impurities like CO or lead bind to the surface of a catalyst, preventing it from functioning.
What is an aromatic compound?
A compound that contains a benzene ring.
What is an aliphatic compound?
A compound that does not contain a benzene ring.
What is a sigma bond?
A bond formed by head-on overlap of orbitals with maximum electron density along the axis.
What is a pi bond?
A bond formed by sideways overlap of p orbitals; found in double bonds and weaker than sigma bonds.
Why can’t atoms rotate around double bonds?
Because pi bonds restrict rotation.
What are structural isomers?
Compounds with the same molecular formula but different structures.
