Week 4 - Kinetics Flashcards by Katherine w

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

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What does kinetics refer to

How fast a reaction proceeds

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what is rate constant k (lowercase)

indicated how fast a reaction is e.g. k=10^5
indicates the time to get to equilibrium

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What is Kc

Equilibrium constant - ratio of the concentrations of the products and reactants - can only be measured at equilibrium

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What is the units for the rate (k)

mol/Ls
Moles per liter seconds

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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.

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What does RDS stand for

Rate determining step

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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

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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

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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

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What are reaction orders

The coefficient of the reactants determines reaction order. E.g. [A]^1 = first order with respect to A

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What is a first order reaction

when the rate changes proportionally with the concentration of the reagent (1 for 1)

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What is the overall reaction order/ overall molecularity

the sum of all of the individual orders

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Reactants

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Transition state

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Products

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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