Flashcards in Gen. Chem 2 Deck (8):
Kinetics is the study of reaction rate. In other words, how quickly the reaction proceeds. This is usually measured in terms of how fast the reactants disappear by tracking changes in the concentration of the reactants as a function of time (i.e., Molarity/second ; M/s).
By contrast, the thermodynamics of a reaction reflect the potential reactivity (for example, given infinite reaction time) and includes all measurements of energy flow and relative stability. Thermodynamics produces the quantities ∆H, ∆G, ∆S, Keq and so forth.
For a reaction to occur:
1. Reactants must collide with enough energy to overcome the energy of activation.
2. Reactants must be in the correct spatial orientation.
Measured as change in molarity of the reactants per second (M/s)
Assume the following:
1. Reactions only proceed forward (ignore reverse reaction)
2. Only consider the first few seconds of the reaction when there is high concentrations of each reactant and any catalysts (e.g. enzyme)
Rate Law Exponents
False idea that exponents are given by coefficients in balanced chemical equation.
Exponents equal the ORDER of each reactant.
Only if specifically told that the reaction is ELEMENTARY do the coefficients equal the exponents in the rate laws.
Always assume they don't.
To calculate ORDER of each reactant using experimental data:
1. Find 2 trials where [reactants] in question CHANGED, but all other parameters remained constant (concentration of other reactants, temperature, pressure, etc)
2. Note factor by which [reactant] changed
3. Note factor by which RATE changed across those same 2 trials.
4. Find Y in X^Y=Z
X=factor by which [reactant] changed
Z= factor by which rate changed
Y= order of the reactant
OVERALL ORDER OF REACTION= sum of exponents in the rate law.