Flashcards in General Chemistry- Chemical Kinetics Deck (138)
Reactions can be __________ or ________.
What determines whether a reaction will occur by itself or with outside help?
The change in Gibbs free energy (/\G)
If a reaction is spontaneous, does it mean it will run quickly?
Every biochemical reaction that enables life proceeds, how?
So slowly that, without the aid of enzymes and other catalysts, measurable reaction progress might not actually occur over the course of an average human lifetime.
Enzymes like other catalyzed reactions, ca be what and experience what?
Can be saturated and experience a maximal turnover rate.
What is the mechanism of a reaction.
Many reactions proceed by more than one step, the series of which is known as the mechanism of a reaction.
The sum of the mechanism of a reaction gives what?
The overall reaction
Knowing the accepted mechanism of a reaction may help explain what?
Position of equilibrium
What is an intermediate?
The molecule A, B, which does not appear in the overall reaction
Why might intermediates be difficult to detect?
They may be consumed almost immediately after they are formed
What is the rate-determining step?
The slowest step in any proposed mechanism
Why is it called the rate determining step?
It acts like a kinetic bottleneck, preventing the overall reaction from proceeding any faster than that slowest step.
What does the collision theory of chemical kinetics state?
The rate of a reaction is proportional to the number of collisions per second between the reacting molecules
What does the collision theory of chemical kineticcs suggest?
Not all collisions result in a chemical reaction
What is an effective collision according to the collision theory of chemical kinetics?
The molecules collide with each other in the correct orientation and with sufficient energy to break their existing bonds and form new ones.
What is the activation energy?
The minimum energy of collision necessary for a reaction to take place.
What is another name for activation energy?
The energy barrier
Do all colliding particles have enought kinetic energy to exceed the activation energy?
Only a fraction of the colliding particles have enough energy to exceed the activation energy
Are all collisions effective, according to the collision theory of chemical kinetics?
Only a fraction
What equation can express the rate of a reaction?
What do the letters represent in the equation for rate of a reaction?
Z: the total number of collisions occuring per second
f: The fraction of collisions that are effective
What is the arrhenius equation?
What do the letters represent in the Arrhenius equation?
k: The rate constant of a reaction
A: The frequency factor
Ea: The activation energy of the reaction
R: the ideal gas constant
T: Temperature in Kelvins
What is the frequency factor?
A measure of how often molecules in a certain reaction collide, with the unit S^-1
What is another name for the frequency factor?
The attempt frequency
What is important when studying the Arrhenius equation?
Not the calculation, but the relationships between the variable and the exponent rules that govern equations.
In the Arrhenius equation, as the frequency factor increases, what happens?
The rate constant of the reaction also increases in a direct relationship
In the arrhenius equation, if the temperature of a chemical system were to increase to infinity, what would happen?
The value of the exponent would have a magnitude less than 1
Does the rate constant decrease as a result of the temperature of a chemical system increasing to infinity in the Arrhenius equation?
No, as the magnitude of the exponent get smaller, it actually moves from a more negative value towards zero