Week 4 - Kinetics Flashcards
Where is kinetics used in dentistry
- kinetics of resin composites and how fast they set
- degradation kinetics of API in drugs (how they store)
- enzyme suppression treatment designed to reduce pocket depth
What does kinetics refer to
How fast a reaction proceeds
what is rate constant k (lowercase)
- indicated how fast a reaction is e.g. k=10^5
- indicates the time to get to equilibrium
What is Kc
Equilibrium constant - ratio of the concentrations of the products and reactants - can only be measured at equilibrium
What is the units for the rate (k)
mol/Ls
Moles per liter seconds
What are elementary steps
In chemical reactions the ‘real process’ occurs in elementary steps, where the sum of the elementary steps to give the balanced equation.
What does RDS stand for
Rate determining step
What is the RDS
The the elementary step in a chemical reaction which requires the highest amount of energy (has the larger energy barrier for it to react) and it determines the rate law.
The slowest step, which determines the overall rate and molecularity of the reaction.
The rate determining step is the slowest elementary step of a chemical reaction it determines the overall rate and molecularity. The RDS is the elementary step with the largest energy barrier (activation energy). It is also used to determine the rate law as it is the slowest elementary step in the reaction
What is the Molecularity of a step
The number of reactants in an elementary step
E.g.
A –> B = unimolecular
C + B –> D = Bimolecular RDS
What is an intermediate
Species which is produced in the middle of a multi step reaction.
It is the lowest point in energy between two consecutive elementary steps. The reaction intermediate is located as the ‘dip’ between two elementary steps within the reaction and is a species which appears in the mechanism of a reaction but not in the final balanced equatio
What are reaction orders
The coefficient of the reactants determines reaction order. E.g. [A]^1 = first order with respect to A
What is a first order reaction
when the rate changes proportionally with the concentration of the reagent (1 for 1)
What is the overall reaction order/ overall molecularity
the sum of all of the individual orders
Reactants
Transition state
Products
What is the effects of temperature on the rate of reaction
Temp Increase
- Increases the number of particles with sufficient activation energy
- Increases the kinetic energy of the particles hence increasing the number of successful collisions
- increases overall rate of reaction
What is this equation and what do the letters stand for
ArrheniT = temperature in kelvin
R = Gas constant
Ea = activation energy (J/mol)
e = exponential
k = reaction constant
A = frequency factor us Equation
What are the units for activation energy
J/mol
Impact of high activation on rate
High Ea = small k (by Arrhenius equation = slow rate of reaction
What is the rough rule for change of temperature on rate
For reactions happening at room temperature the rate of reaction doubles for ever 10 degrees rise in temperature
What is the initial rate
rate of reactions at the very beginning of the reaction
What is the instantaneous rate
rate of reaction at any specific point in time hence it will always be different depending on what time you measure it - changes all the time until equilibrium
What is the average rate
the average rate of reaction over the whole reaction
What does this equation let you calculate
Differential Rate Law
The rate at a specific moment (instantaneous)
where d = delta (change in)
where there’s a -1 since the rate is a decrease in reactants over time
What does this equation let you find
General Rate Law
Lets you predict the rate of the reaction when provided with the concentrations
What does this equation let you find
Integrated Rate Law
Lets you calculate the rate over the period t, used to work out changes in concentrations or how long a reaction will take
*will mainly focus on first order reactions
What does this equation let you find
Half life
What are catalysts and their function
Catalyst are reagents added to a reaction in non-stoichiometric amounts
They
- increase the rate of reaction
- Lower Ea for RDS
- Are not consumed after a reaction
- Don’t affect K/ the yield
Catalyst provide a different pathway for a reaction to occur which reduces the activation energy of the reaction
What are homogeneous catalysts
Catalyst in the same phase/state (solid, liquid) as the reactants
Example of a homogenous catalyst
used in production of acetic acid
What are heterogeneous catalysts
Catalyst in different phases/state (solid, liquid) to the reactants
Example of a heterogeneous catalyst
catalytic converter (solid catalyst) in car exhaust (reactant gases)
What is a pharmaceutical drug
A pharmaceutical or drug is some sort of dosage aimed to diagnose, cure, treat or prevent a disease. They are most commonly seen as tablets (compressed solids)
What is the composition of a tablet
5 - 10% = Active Pharmaceutical Ingredient
80% = Fillers, disintegrants, lubricants, colorants, flavours
10% = Substances that change the nature of the delivery of the API
e.g. compounds which ensure easy disintegration if it needs to move very quickly.
e.g. May be coated to make it acid resistant so it can make it through the stomach
What is an API
Active Pharmaceutical Ingredient - which is the biologically active substance in drug, typically a small organic molecule
- some medications may contain more than one API and APIs from different medications can interfere with each other often resulting in severe complications
What should you consider with API
- some medications may contain more than one API
- APIs from different medications can interfere with each other often resulting in severe complications
What may cause Pharmaceutical drug decomposition
- Light (photodegradation)
- Heat (thermal)
- Redox (oxidation)
- Water (hydrolysis)
How do you calculate the shelf life of a drug
Half life where (90% is remaining
In(9/10)/k = 0.105/k
What is pharmacokinetics
Study of the time line of the drug when it is delivered till when it is removed from the body.
Tracts the adsorption, bioavailability, distribution, metabolism and excretion of the drug
