Rate of reaction

What is rate of reaction determines as

Determined as rate of change in concentration

How is rate expressed

Per unit of time

1/ time

S^-1

Rate of reaction general idea

Increase in product concentration // TIme

Decrease in reactant concentration // Time

Mol dm^-3 s^-1

Instantaneous rate of reaction

• take a tangent on the part of the curve

  • fastest at the start, slows down

How to measure rate

• change in volume of gas

• change in mass

• change in transmission of life

• change in concentration, measure with titrations

• change in concentration using conductivity

• non-continuous method: ‘clock reaction‘

change in volume of gas

• volume against time

• gas syringe

Change in mass

If the reaction gives off gas, doesn’t work with hydrogen, too light

Change in light transmission

• can be done if reactants of products are coloured

• Works by: passing light of a selected wavelength through solution

• As concentration of colour increases, absorbs more light, less light transmitted

Change in concentration using titration

• cannot be done continuously, as reaction continues

• Method of quenching used, otherwise the reaction keeps proceeding

  • stops reaction at a moment in time

Change in concentration

Depends on ions and on their charges

Non-continuous method: ‘clock reaction‘

• time taken to reach a fixed point

  • time is a dependent variable

Maxwell-Boltzmann energy distribution curve

Nature of collisions and the influencing factors

• Kinetic energy causes for particles to collide, breaking and forming new bonds

• influencing factors

  • energy of collision

  • geometry of collision

What is activation energy

the energy required for overcoming the repulsion and breaking bonds to allow reactions

what is transition state

when energy supplied, reactants achieve transition state

Endothermic vs Exothermic

• endothermic - require heat, cool surroundings

• exothermic - release heat, warm surroundings

Maxwell boltzman curve with Ea

What is the geometry of collisions

the orientation of particles

Temp influencing rate of reaction

As temp increase, so does kinetic energy.

more particles collide succesfully

Concentration

as concentration increase, so does rate

• as concentration increase, frequency increases

pressure

• increasing pressure, increase rate of reaction

• higher pressure, compresses gases, increasing concentration, increasing frequency

Surface area

Increasing SA, Increases rate

• allows for more reactions

Catalyst

Provide alternative route, Ea lower

• equal for forwards and backwards reaction