Developing Fuels Flashcards
What is an exothermic reaction and what would the enthalpy level diagram look like?
A reaction that gives out energy and heats the surroundings.
Enthalpy change will be negative, the products are on a higher energy level than the products.
Bond - forming is exothermic!
What is an enthalpy change? What units is it in?
Enthalpy change is the quantity of energy transferred to or from the surrounding environment
KJ mol^-1
What are the standard conditions that allow us to compare enthalpy changes?
298k(25*c)
100kpa(1 atm)
1 mol dm^-3
What volume does one mole of gas at room temperature and pressure take up?
24,000cm^3 or 24dm^3 (hence the equation moles = volume/24)
What is the ideal gas equation?
How can we measure an enthalpy change?
We can measure the energy transferred to or from water surrounding the reaction vessel.
Measuring the change in temperature of the water and its mass allow us to use the equation:
q(KJ) = m(g) x c( 4.18Jg^-1K^-1) x Δt(K) , where the specific heat capacity (c) of water is 4.18Jg^-1K^-1
What is the standard enthalpy change of reaction?
ΔrH⦵298
The enthalpy change when molar quantities of reactants, of proportions stated in the equation, react under standard conditions and in standard states.
What is the standard enthalpy change of combustion?
ΔcH⦵298
The enthalpy change when one mole of a substance is combusted completely in oxygen, in standard conditions and states
They are always exothermic so will always have a negative value
What is the standard enthalpy change of formation?
The enthalpy change when one mole of a compound is formed from its elements, under standard conditions and in standard states.
What is the definition of the standard enthalpy change of neutralisation?
ΔneutH⦵298
The enthalpy change when one mole of hydrogen ions react with one mole of hydroxide ions to form one mole of water, under standard conditions and in solutions of molar concentration
What is an Aromatic compound?
Compounds that contain one or more benzene ring.
What is an Aliphatic compound?
Compounds that do not contain any benzene rings
What is a functional group?
Modifiers that are responsible for the characteristic chemical reactions of molecules
What is a saturated hydrocarbon?
One that doesn’t contain any carbon - carbon double bonds
What is Hess’s law?
The total enthalpy change during the complete course of a chemical reaction is consistent, whether the reaction’s course is over one or several steps.
