Inorganic and physical chemistry - part 3 Flashcards
what is the standard enthalpy of formation?
enthalpy change when one mole of a substance is formed from its elements in their standard states
state the three standard conditions
- per mole
- one atmosphere
- specified temperature (usually 298K)
what is a standard state?
state element is most commonly observed in at standard conditions
what value in degrees Celsius is absolute zero?
-273
what is entropy a measure of?
measure of the degree of disorder in a system
what is the third law of thermodynamics?
at absolute zero, a crystal lattice has a perfect order and zero entropy
what happens to the entropy value as the temperature increases?
entropy increases
what has a greater entropy, a solid or a gas?
a gas
when is a process spontaneous?
when it can take place without being driven by an external force
why can a process be spontaneous?
- entropy increase is so large
- counterbalances the unfavourable enthalpy change
as heat energy is released by a reaction system, what happens to the entropy of the surroundings?
entropy increases
as heat energy is absorbed by a reaction system, what happens to the entropy of the surroundings?
entropy decreases
when is a reaction feasible
reaction tends towards the products side rather than reactants
what is the second law of thermodynamics?
for a reaction to be feasible, the total entropy change for a reaction system and its surroundings must be positive
what must be negative for a reaction to be feasible?
free energy
what is happening to the reaction when (delta)G=0
reaction is at equilibrium
when is the free energy of the system at its minimum value?
at equilibrium
if (delta)G is large and negative, on which side of the reaction will the equilibrium lie?
lies on products
if (delta)G is large and positive, on which side of the reaction will the equilibrium lie?
lies on reactants
what is zero order?
doubling the concentration has no effect on the rate
for a zero order reaction, what is the units of k?
mol l^-1 s^-1
for a first order reaction, what is the units of k?
s^-1
for a second order reaction, what is the units of k?
l mol^-1 s^-1
for a third order reaction, what is the units of k?
l^2 mol^-2 s^-1
