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expression that defines the change in free energy (equation)
ΔG = ΔH – TΔS
The term that describes the change in the concentration of a reactant divided by the change in time of the reaction
Average Reaction Rate
Substance that increases the rate of a chemical reaction without being used up
catalyst
The rate law for the forward one-step reaction A + B --> 3C
R=K[A][B]
the slowest step in a reaction that proceeds in a sequence of steps
rate-determining step
entropy increases when temperature _____________
increases
Overall reaction order for the following rate-law expression
Rate = k[A][B]2[C]3
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two conditions for an effective collision
sufficient energy ad favorable orientation
Batteries and film will stay fresh longer if they are kept in a refrigerator or freezer
low temperature, particles have low kinetic energy, fewer collisions, slower reaction rate
Species that appear in some steps but do not appear in the net equation.
Intermediate
Suppose that the following chemical reaction A + B + 2D → E takes place in a two-step mechanism.
Step 1: (fast) A + B → C
Step 2: (slow) C + 2D → E
Identify the rate-determining step and write an acceptable rate law. Identify the intermediate.
Rate determining step: step 2 the slow one
Intermediate: C
Rate law for rate determining step: R=K[C][D]2
Overall order = 2 + 1 = 3
It is found at the peak of the energy profile graph
Activated-Complex
the phase state that has the highest entropy
gas
it is unique, doesn't change with change in concentration, but changes with change in temperature
Specific Rate Constant K
reaction mechanism
ΔH is positive and ΔS is negative
Non-spontaneous reaction
Short-lived unstable structure formed during a collision
Activated-complex
Free energy change depends on
temperature, change in enthalpy and change in entropy
Calculate ΔGsystem for the following process, and state whether the process is spontaneous or nonspontaneous. ΔHsystem = –150 kJ, T = 200 K, ΔSsystem = +2.00 kJ/mol•K
ΔG= ΔH - TΔS
ΔG= -150 - (200 x 2) = -150 - 400 =-550
If doubling the concentration of a reactant doubles the rate of the reaction, the concentration of the reactant appears in the rate law with
exponent of 1 (order of reaction = 1)
For the reaction A(g) + B(g) + energy --> 3C(g) + D(g),
Is entropy change positive or negative? Is enthalpy change positive or negative?
Entropy change = positive (more moles of gas in the products side)
Enthalpy change = positive (energy in reactants side endothermic)
On the energy profile this is measured from the reactants to the activated complex
activation energy
Lowers the activation energy
Catalyst
increases the rate of a reaction
increasing temperature
increasing surface area (use powder instead of lumps)
increasing concentration
Adding a catalyst
A reaction is zero order in reactant A and second order in reactant B. If both concentrations are doubled the rate will
quadruple (increase by a factor of 4)