energetics Flashcards
what is the standard enthalpy change of reaction?
the enthalpy change when molar quantities of reactants as specified by the chemical equation react to form products at 298K and 1 bar
what is the standard enthalpy change of formation?
the enthalpy change when 1 mole of substance is formed from its constituent gaseous elements at 298K and 1 bar
what is the standard enthalpy change of combustion?
the heat evolved when one mole of a substance is completely burned in excess oxygen at 298K and 1 bar
what is the standard enthalpy change of atomisation of an element?
the energy required when one mole of gaseous atoms is formed from the element at 298K and 1 bar
what is the standard enthalpy change of atomisation for a compound?
the energy required to convert 1 mole of the compound into gaseous atoms at 298K and 1 bar
what is the standard enthalpy change of neutralisation?
the enthalpy change when 1 mole of water is formed in a neutralisation reaction between an acid and a base at 298K and 1 bar
what is lattice energy?
it is the heat evolved when 1 mole of ionic solid is formed from its constituent gaseous ions
what is bond energy?
the energy required to break 1 mole of a covalent bond in the gaseous state
what is the formula for the weighted average initial temperature?
[(temp of x)(vol of x) + (temp of y)(vol of y)]/(total v)
what is the formula to determine heat change of a reaction?
q=mcT
what is the formula to determine enthalpy change?
enthalpy change = q/n
if exothermic, add a (-) at the front
what is the method to find lattice energy?
borne haber cycle
what is required for a borne haber cycle? (if finding lattice energy)
- enthalpy change of formation of ionic solid
- enthalpy change of atomisation of constituent atoms
- bond energy for non metal - take note of coefficients
- ionisation energy for metal (depending on number of electrons lost)
- electron affinity of non metal (first is negative, subsequent all positive)
what is first electron affinity?
the enthalpy change when 1 mole of electrons is added to 1 mole of gaseous atoms to form 1 mole of singly charged gaseous anions
what is first ionisation energy?
the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of singly charged gaseous cations
what is the standard enthalpy change of hydration?
the enthalpy change when 1 mole of free gaseous ions is completely dissolved in an infinite volume of water at 298K and 1 bar
what is the enthalpy change of solution?
the enthalpy change when 1 mole of solute is completely dissolved in an infinite volume of solvent at 298K and 1 bar
what is entropy?
a measure of randomness or disorder in a system, reflected in the number of ways that particle and their energy can be distributed - greater disorder/ randomness, greater entropy
how can we predict change in entropy?
- change in temperature - temp increase, k.e. increase, more ways to disperse the particles and their energy, entropy increase
- change in phase - solid to liquid: particles move more freely in the liquid state, more ways to distribute particles and their energy, entropy increase
- change in no. of particles - no. of gaseous particles increase, no. of ways particles and their energy can be distributed increase, entropy increase
- mixing of particles - particles mixed, volume allowed to occupy increase, no. of ways particles and their energy can be distributed increase, entropy increase (essentially, volume increase, entropy increase)
what is a spontaneous process?
it is a process that takes place naturally in the direction stated
what is gibbs free energy change of reaction?
ΔG = ΔH - TΔS
what does the value of ΔG imply?
ΔG<0: reaction is spontaneous (exergonic)
ΔG>0: reaction is not spontaneous (endergonic)
ΔG=0: reaction is in equilibrium
