Thermodynamics Flashcards
Do exothermic reactions have positive or negative enthalpy changes
Negative enthalpy changes
heat energy is given out
Give the definition of bond dissociation enthalpy
enthalpy change when all the bonds of the same type in 1 mole of gaseous molecules are broken
What is the equation representing the enthalpy change of atomisation for NaCl(s)
NaCl(s) -> Na(g) + Cl(g)
Define first ionisation energy
enthalpy change when 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms
Define first electron affinity
enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms
Is lattice formation an exothermic or endothermic process
exothermic
Explain why theoretical lattice enthalpies are often different from experimental determined lattice enthalpies
theoretical lattice enthalpy calculations are based on the ionic model that assumes all ions are spherical
most ionic compounds have covalent character
the more polarisation the more covalent character
Describe the two steps that occur when an ionic lattice dissolves in water
the bonds between ions break to give free ions- endothermic
bonds between the ions and water are made- exothermic
Do soluble substances have exothermic or endothermic enthalpies of solution, in general
exothermic
What does entropy mean
how much disorder there is
a measure of the number of ways that particles can be arranged and the number of ways that energy can be shared out between particles
which has a greater entropy
1 mole of NaCl(aq) or 1 mole of NaCl(s)
NaCl(aq)
which has a greater entropy
1 mole of Br2(l) or 1 mole of Br2(g)
Br2(g)
which has a greater entropy
1 mole of Br2(g) or 2 moles of Br2(g)
2 moles of Br2(g)
What is the formula used for finding the entropy change of a reaction
delta s = products - reactants
what does delta G stand for
free energy change
