QUARTER 2 EXAM Flashcards
The area of chemistry concerned with speed, or rates, at which a chemical reaction occurs
CHEMICAL KINETICS
refers to the rate of a reaction, or the reaction rate, which is the change in the concentration of a reactant or a product with time (M/s)
Kinetics
Any reaction can be represented by the general equation:
Reactants → Products
The speed at which a chemical reacts is called reaction rate
A + B → C
THE RATE OF REACTION
__________ helps determine how reactions occur, specifically the order in which chemical bonds are broken or formed.
Chemical kinetics
Reactants typically _____ in concentration over time, while products ______.
decrease ; increase
The more readily molecules collide, the faster they react. Smaller particles with larger surface areas react faster.
In order to react, molecules must come in contact with each other
The more homogeneous the mixture of reactants, the faster the molecules can react
PHYSICAL STATE
FACTORS AFFECTING THE RATE OF REACTION
PHYSICAL STATE
REACTANT CONCENTRATION
REACTION TEMPERATURE
CATALYST
Higher concentration means more particles are available to collide, increasing the reaction rate.
As reactant concentration increases, the frequency with which the reactant molecules collide increase, leading rates
REACTANT CONCENTRATION
Increasing temperature raises kinetic energy, making particles move faster and collide more often.
Reaction rates generally increase as temperature is increased
REACTION TEMPERATURE
A _____ speeds up the reaction by changing the reaction mechanism but is not consumed in the process.
catalyst
For a reaction to occur:
Particles must _____
_________ to break bonds.
The correct _________ to form new bonds.
- collide
- Sufficient energy
- orientation
TRUE OR FALSE
The greater the number of collisions the slower the rate.
false
The greater the number of collisions the faster the rate.
true or false
The more molecules present, the greater the probability of collision and the faster the rate.
true
In order for reaction to occur the reactant molecules must collide in the correct orientation and with enough energy to form products
true or false
true
Reactant rates are denoted with a negative sign to show ______, while products are positive
depletion
At any specific time, the rate at which a reaction is proceeding is known as its ________
instantaneous rate.
The rate at one single/particular point in time
Instantaneous Rate
Rate calculated between 2 points.
: the average between 2 instantaneous reaction rates.
Average Rate:
A constant of proportionality between the reaction rate and concentration of reactant
RATE CONSTANT
It remains constant regardless of the time point; it does not change over the course of the reaction.
RATE CONSTANT
The exponents x and y specify the relationships between the concentrations of reactants A and B and the reaction rate.
RATE LAW
For any reaction, the rate law must be determined experimentally
true or false
true
A _______reaction is one whose rate depends either on a reactant concentration raised to the second power on the concentrations of two reactants each raised to the first power
second-order
Rate expressions are not always determined by experiments
true or false
false
Rate expressions are always determined by experiments
It expresses the relationship of the rate of a reaction to the rate constant and the concentration so the reactants raised to some papers:
aA+bBcC+dD
rate law
A ______ reaction is one whose rate depends on the concentration of a single reactant raised to the first power
first-order
Rate depends on the concentration of one reactant
first order
Rate depends on the concentration of one reactant squared or two reactants
second-order
is one which rate of disappearance of A is independent of [A]
zero-order reaction
Rate is independent of the concentration of reactants
zero order
______ Order: The initial rate decreases eightfold when the concentration of the reactant is doubled (1:3 relationship).
Third
_____ Order: The initial rate quadruples when the concentration of the reactant is doubled (1:2 relationship).
Second
_____ Order: No effect on the initial rate when the concentration of the reactant is changed.
Zero
____ Order: The initial rate doubles when the concentration of the reactant is doubled (1:1 relationship).
First
The time required for the concentration of a reactant to reach half its initial value
THE HALF-LIFE (T ½)
A convenient way to describe how fast a reaction occurs
THE HALF-LIFE (T ½)
Drugs with _____ half-lives take longer to take effect but have prolonged action, allowing for less frequent dosing (e.g., once daily, weekly, or monthly).
longer
Drugs with _______ half-lives act quickly but wear off rapidly, necessitating multiple doses throughout the day.
shorter
Drugs reach a _______—where the amount of drug eliminated equals the amount administered—typically after five half-lives. This is crucial for maintenance medications (e.g., for hypertension, diabetes, and antibiotics).
steady state
Constant quantity per time
For every minute, 5mg of the drug is eliminated
THE HALF-LIFE: ZERO ORDER
The concentration of the reactant decreases by one-half in each of a series of regularly spaced time intervals, each interval equal to +½
THE HALF-LIFE: FIRST ORDER
It is used to calculate the remaining concentration of a substance after a given time period.
INTEGRATE RATE LAW: 1ST ORDER
Is the minimum amount of energy required for a chemical reaction to process. It is essentially a barrier that molecules overcome before they can react and form products.
ACTIVATION ENERGY
Release energy, making the energy of the products lower than that of the reactants. The activation energy in these reactions is less compared to the total energy released.
EXOTHERMIC
Constant fraction per time unit
For every minute, 5% of the drug is eliminated
THE HALF-LIFE: FIRST ORDER
The final state or endpoint of the reaction.
PRODUCTS
The starting substances in a reaction.
REACTANTS
Absorb energy, resulting in products with higher energy than the reactants. The activation energy here is greater than the overall energy absorbed.
ENDOTHERMIC
The energy barrier that must be overcome for a reaction to proceed.
Energy Activation (Ea)
The intermediate state between the reactants and products, where bonds of the reactants are breaking, and bonds of the products are forming.
Transition State (AB)
tell you the components of the overall reaction; how will the reaction proceed.
REACTION MECHANISM
These are the individual, simple steps that make up the overall reaction. They can be unimolecular (involving a single molecule) or bimolecular (involving two molecules)
Elementary Steps
These are species that are formed during the reaction but are not present in the overall equation. They are often highly reactive and short-lived
Intermediates
The slowest step in a reaction mechanism, which dictates the overall rate of the reaction. The activation energy for this step is higher than that of other steps, making it the most crucial step in controlling the reaction rate.
Rate-Determining Step (RDS)
The energy barrier that must be overcome for each elementary step to proceed
Activation Energy
_______ refers to the number of molecules or ions that collide simultaneously to form a product in a single elementary step of a reaction mechanism. It is an important concept in understanding the kinetics of chemical reactions.
Molecularity
true or false
Higher molecularity beyond termolecular are very rare due to the low probability of molecules colliding simultaneously
true
A reaction involving a single molecule
UNIMOLECULAR
A reaction involving a two molecules
BIMOLECULAR
A reaction involving a three molecules
TERMOLECULAR
A catalyst that is present in the same phase as the reactants in a reaction mixture
HOMOGENEOUS CATALYST
It provides an alternative reaction pathway with lower activation energy, allowing the reaction to occur faster.
CATALYSIS
Is a substance that increases the rate of a chemical reaction without itself being consumed
CATALYSIS
An advantage if heterogenous catalysis is that the catalyst mixes into the reaction mixture, allowing a very high degree of interaction between catalyst and reactant molecules
true or false
false
An advantage if homogenous catalysis is that the catalyst mixes into the reaction mixture, allowing a very high degree of interaction between catalyst and reactant molecules
They allow for an increase in reaction rate without an increase in temperature
HOMOGENEOUS CATALYST
Mixes well with reactants, ensuring a high degree of interaction, thus increasing the reaction rate without the need for increased temperature.
HOMOGENEOUS CATALYST
This involves the use of catalyst in a different phase from the reactants
Liquids or gases
HETEROGENEOUS CATALYST
One or more of the reactants are absorbed on to the surface of the catalyst at the active sites
HETEROGENEOUS CATALYST
After absorption, the reaction happens and the product molecules are desorbed
HETEROGENEOUS CATALYST
Good catalyst needs to absorb the reactant molecules strongly enough for them to react, but nor so strongly that the product molecules stick more or less permanently to the surface
true or false
true
A natural catalyst that accelerates biological reactions in organisms.
ENZYMATIC CATALYST
The enzyme’s active site is highly specific, following a lock-and-key model. Only substrates that match the active site can bind, lowering activation energy and facilitating the reaction. After the reaction, the products are released.
ENZYMATIC CATALYST
Key
They bind to the active side of the enzyme, the lock, as it is highly selective, will allow the lowering of activation energy
Substrate
Hydrolyze the bonds, and break molecules into smaller components by adding water
Hydrolases
Break the bonds and catalyze the reaction allowing the reaction to proceed, releasing the product
Enzymes’ active side are very specific for a specific substrate
Enzyme-Substrate Complex
Catalyze oxidation-reduction
Oxidoreductases
Catalyze the transfer of molecules
Transferases
Catalyze the cleavage of bonds without the use of water or oxidation; responsible for forming octaval bonds
Lyases
Help the rearrangement of atoms
Isomerases
Join two or more molecules together
Ligases
The state of a chemical reaction when the concentrations of the products and reactants are unchanged over time
CHEMICAL EQUILIBRIUM
It is also known as Dynamic Equilibrium
CHEMICAL EQUILIBRIUM
When a reaction reaches equilibrium, the rate of the forward reaction equals the rate of the backward reaction.
Equilibrium Condition:
all reaction can have an equilibrium
true or false
Only a reversible reaction can have an equilibrium
false
Reactions at equilibrium are represented by a______________, indicating the reaction is reversible
double-headed (equilibrium) arrow (⇌)
Reactants (A and B) combine to form products (C and D).
Forward Reaction
Products (C and D) recombine to reform the reactants (A and B).
Reverse Reaction
FACTORS AFFECTING EQUILIBRIUM
Temperature, Pressure, and Concentration
When a system is at equilibrium, a constant value is established by the multiplicative product of the concentrations of the products’ concentrations (each raised first to the power of its coefficient), then divided by the multiplicative product of the reactants’ concentrations (each raised first to the power of its coefficient).
- Law of Mass Action (Cato Maximilian Guldberg and Peter Waage)
A ____________ has everything present in the same phase. The usual examples include reactions where everything is a gas, or everything is present in the same solution.
homogeneous equilibrium
The _________ represents the ratio of the concentrations of the products raised to their stoichiometric coefficients to the concentrations of the reactants raised to their stoichiometric coefficients.
equilibrium constant Kc
All reactants and products are in the same phase (all solid, all gas, all aqueous, or all liquid).
homogeneous equilibrium
A ____________ has things present in more than one phase. The usual examples include reactions involving solids and gases, or solids and liquids.
Reactants and products are in different phases (e.g., gas, aqueous).
heterogeneous equilibrium
true or false
for equilibrium, the value of K remains constant if temperature is unchanged.
true
true or false
equilibrium is not affected by: Changes in pressure or addition of a catalyst.
true
A K value between 0.01 and 100 indicates that the reaction is _________ or _______
incomplete or reversible.
t or f
The equilibrium constant always has the same value (provided you don’t change the temperature), irrespective of the amounts of A, B, Cand D you started with. It is also unaffected by a change in pressure or whether or not you are using a catalyst.
t
Measures the relative amount of products and reactants present during a reaction at a particular point in time.
THE REACTION QUOTIENT
Aids in figuring out which direction a reaction is likely to proceed, given the pressures or the concentrations of the reactants and the products.
THE REACTION QUOTIENT
If a chemical system at equilibrium experiences a change in concentration, Temperature or pressure (either the reactant or product side), the equilibrium will shift in order to minimize that change.
LE CHATELIER’S PRINCIPLE
helps to predict what a change in temperature, concentration or pressure will have on the position of the equilibrium in a chemical reaction.
LE CHATELIER’S PRINCIPLE
If the concentration of a substance is increased, the equilibrium will shift so that the concentration increase.
true or false
false
If the concentration of a substance is increased, the equilibrium will shift so that the concentration decreases.
If the concentration of a reactant is increased, the equilibrium would shift in the direction of the reaction that used up the reactants
true or false
true
If the concentration is increased, the equilibrium will shift so that the concentration decreases.
true or false
true
When the pressure of a system increases, there are less particles in a particular space. The equilibrium will shift in a direction that reduces the number of gas particles so that the pressure is reduced.
true or false
false
When the pressure of a system increases, there are more particles in a particular space. The equilibrium will shift in a direction that reduces the number of gas particles so that the pressure is reduced.
The chemical system must be in equilibrium first.
t or f
t
The changes will involve increasing or decreasing something which affects the equilibrium.
t or f
t
The old equilibrium will not change itself without rearranging the Keq value.
t or f
The old equilibrium will change itself without rearranging the Keq value.
Keq value changes when pressure is involved.
t or f
Keq value changes when temperature is involved.
false
If something is increased, the induced change will be for something to decrease.
true or false
true
