energetics Flashcards
State the Enthalpy change of Atomisation
the enthalpy changes when one mole of a gaseous atom is formed from its elements under standard conditions
state Hess’s Law
The Total ethanol change in a chemical reaction is independent of the route by which the chemical reaction takes place as long as the initial and final conditions are the same
what does Dleta Hr Mean?
change in Enthalpy
what is the indirect rout to get to products of a reaction?
for elements to first be formed into reactants
What is the equation for finding an enthalpy change in a reaction?
Q = m c T
Where:
Q = heat / thermal energy absorbed/released
T = Temperature in Kelvin (theta for centigrade)
m = mass of water (g)
c = specific heat capacity of water
what is the Haber Process?
the formation of ammonia in the production of fertilizers
What is Calorimetry?
a technique used to measure changes in enthalpy of chemical reactions
what is specific heat capacity?
the energy required to increase the temperature of 1g of a substance by 1 degree centigrade
what is bond dissociation energy?
the amount of energy required to break one mole of a specific covalent bond in gas phase
when calculating bond energy what does delta Hr equal?
enthalpy change of bonds broken + enthalpy change for bonds formed
define combustion
burning in air/oxygen
state conditions for standard enthalpy change
101.325kpa (pressure)
298K (temp)
each substance involved is in its normal state
state the standard enthalpy change of reaction
the enthalpy changes when the reactants in the stoichiometric equation react to give the products under standard conditions
(delta Hr)
state the standard enthalpy change of formation
the enthalpy changes when one mole of a compound is formed from its elements under standard conditions
(delta Hf)
state the standard enthalpy change of combustion
the enthalpy changes when one mole of a substance is burned in excess of oxygen under standard conditions
(delta Hc)
is combustion endo- or exo- thermic
exothermic
state the standard enthalpy change of Nutralisation
the enthalpy changes when one mole of water is formed by reacting an acid and alkali under standard conditions
enthalpy change of reactions = …
products - reactants
True of Falce. exothermic reactions are thermodynamically possible
True. IE they can happen spontaneously
what happens in transition state?
bonds are partially broken and partially formed (very temporary and very unstable)
define enthalpy
the total chemical energy in a body or heat content
