Chemical Kinetics Practice Flashcards

Vocabulary-style flashcards based on lecture notes covering fundamental concepts of chemical kinetics including rate calculations, order, molecularity, and factors affecting reaction speed.

Chemical Kinetics

The study of how fast a chemical reaction takes place and the different factors affecting the rate of the chemical reaction.

Rate of Reaction

The rate of change in concentration with time of any chemical species taking part in a chemical reaction, expressed as $\text{mol L}^{-1} \text{ time}^{-1}$ or $\text{mol dm}^{-3} \text{ time}^{-1}$.

Average Rate

The total change in concentration divided by the total time taken; it corresponds to the slope of the chord on a concentration versus time curve.

Instantaneous Rate

The rate of reaction at a particular instant determined by drawing a tangent at time $t$ on a concentration versus time curve, represented as $\frac{dc}{dt}$.

Initial Rate

The instantaneous rate of a chemical reaction at $t=0$, calculated as the slope of the tangent at the start of the reaction.

Differential Rate Law

An expression where the rate of reaction is equated to the rate of appearance or disappearance of a species divided by its stoichiometric coefficient in the balanced chemical reaction.

Rate Law

An experimental expression in which the reaction rate is given in terms of molar concentrations of reactants, with each term raised to a power that may or may not be the same as its stoichiometric coefficient.

Rate Constant ($k$)

A proportionality constant in the rate law, also known as the specific rate of a reaction, which is independent of reactant concentration but changes with temperature.

Order of Reaction

The sum of the powers of the concentration terms of the reactants as they appear in the rate law; it is an experimental value that can be zero, fractional, or an integer.

Molecularity

The number of molecules that react in an elementary step of a reaction; it is a theoretical whole number and is only defined for elementary reactions.

Elementary Reaction

A chemical reaction that occurs in a single step with a defined molecularity.

Rate Determining Step

The slowest step in the mechanism of a complex reaction, used to experimentally calculate the overall order of that reaction.

Activation Energy

The minimum energy required for a chemical reaction to occur; reactions with lower values of this energy proceed at faster rates.

Specific Rate of a Reaction

The value of the rate constant $k$ at a given temperature when the concentration of all reactants is unity.

Unit of Rate Constant ($k$)

For a reaction of order $n$, the unit is calculated as $(\text{concentration})^{1-n} \text{time}^{-1}$.