Review of Chemical Reactions and Kinetics

Need for Speed

50

The intensive measure of how fast a chemical species is consumed or formed, typically expressed as moles per unit volume per unit time.

Rate of reaction

100

By standard kinetic convention, the rate of formation (r_A) is defined so that a reactant undergoing consumption will always have a value with this mathematical sign.

Negative

150

A single-step reaction whose empirical rate equation corresponds exactly to its stoichiometry.

Elementary reaction

200

A reaction where the stoichiometric equation does not match the kinetic rate law, indicating the process occurs via a multi-step mechanism.

Non-elementary reaction

Law & Order: Kinetic Unit

50

This parameter is defined as the sum of the concentration exponents in a power-law rate equation.

Overall reaction order

100

For this specific reaction order, the half-life is completely independent of the reactant's initial concentration.

First-order

150

The standard SI units for the specific reaction rate constant (k) of a zero-order reaction.

mol/(L.s)

200

For a purely second-order reaction involving a single reactant (2A --> products), the half-life is inversely proportional to this specific starting value.

Initial concentration (C_A0)

Things Are Heating Up

50

This fundamental exponential equation relates the specific reaction rate constant to absolute temperature.

Arrhenius equation

100

This parameter represents the minimum energy threshold that reacting molecules must overcome upon collision to successfully form products.

Activation energy

150

According to Arrhenius theory, plotting the natural log of the rate constant, ln(k), against the reciprocal of temperature, 1/T, yields a straight line with this slope.

-E_a/R

200

In the Arrhenius equation, the dimensionless exponential term e^-E_a/RT physically represents the fraction of molecular collisions that possess this.

Sufficient energy to react

(or Energy higher or equal to E_a)

It's Complicated

50

Reactions where a single reactant decomposes to form multiple different products simultaneously, creating competition for the reactant.

Parallel reaction

100

Reactions that occur in consecutive steps, such as reactant A forming intermediate R, which then reacts to form product S.

Series reaction

150

A chemical process where one of the reaction products acts as a catalyst, causing the overall reaction rate to slowly increase as product accumulates before eventually dropping.

Autocatalytic reaction

200

For the elementary series reaction A --> R --> S, the maximum concentration that the intermediate species R can reach depends strictly on this specific ratio.

Ratio of the rate constant (k₂/k₁)

Do the Math!

50

For a zero-order reaction (A --> products) with k = 0.1 mol/(L.s) and C_A0 = 1.0 mol/L, this is the concentration of A remaining after 5 seconds.

0.5 mol/L

100

For a first-order liquid-phase reaction with a rate constant k = 0.693 min^-1, calculate the half-life (t_1/2) of the reactant in minutes.

1 min

150

A second-order reaction (2A --> products) has C_A0 = 1.0 mol/L and k = 0.5 L/(mol.min). Calculate the time in minutes required to reach 50% conversion.

2 min

200

An Arrhenius plot of ln(k) versus 1/T yields a slope of -5000 K. Using R = 8.314 J/(mol.K), this is the activation energy E_a in kJ/mol.

41.57 kJ/mol