Rates Of Reaction Flashcards
What is rate of reaction and what are the factors that affect it?
The change in concentration of a reactant or product in a given time.
Concentration, pressure, temp, surface area, catalyst.
What is activation energy?
The minimum energy required to start a reaction by breaking bonds.
What is the collision theory?
Chemical reaction will only take place when reacting molecules collide with enough energy to overcome the activation energy and molecules collide in the correct orientation.
What is the affect of concentration on rate of reaction?
If increases, more particles per unit volume, more crowded so more frequent successful collisions, increasing rate of reaction.
What is the effect of pressure on rate of reaction?
Pressure increases, molecules closer together as theres more particles per unit volume. More frequent successful collisions and more collisions with energy greater than activation energy. Increasing rate of reaction.
How do you calculate rate of reaction?
Draw tangent.
Find gradient.
Gradient= changing in reactant or product / change in time.
How can the progress of chemical reaction be followed?
Monitoring removal of reactant, following formation of product. And look at physical state symbols.
Also look at pH, colour and volume.
What are the methods ypu could use to determine rate at which gas is produced?
-monitor vol gas produced at regular intervals using a gas collector (upside down cylinder in bath with a magnesium dioxide catalyst and add bung to beaker)
- monitoring loss of mass of reactants using balance ( measure mass initially then measure at regular intervals.)
What is a catalyst and its role?
Increases rate of chemical reaction without being used up in process.
Lowers activation energy by providing an alternate route with a lower energy. Rate reaction increases as molecules reach activation energy faster and more molecules have an energy equal to or more than Ea and more frequent successful collisions.
What are different types of catalysts?
Homogenous catalyst ( the same physical state as reactants) : e.g. catalyst used to speed up an aqueous reaction is aqueous I- ions.
Heterogeneous catalyst ( different physical state) : happens at surface of the catalyst so increasing SA of catalyst can help increase RofR .e.g. haber process.
Why are catalysts used in industry?
- reduce energy costs as they offer lower temps reducing the demand for energy
- reducing CO2 emissions as less fossil fuels need to be burned so more sustainable.
- some used to make it more effective improving % yield and atom economy of processes, reducing waste.
- catalysts have great economic importance.
What does the Boltzmann distribution show on gas and liquid?
Some molecules are moving fast and have higher energy.
Some molecules move slowly and have less energy.
Majority molecules have an average energy.
What are the important features of a Boltzmann distribution?
- area under curve is equal to total number of molecules in sample.
- no molecules in system with zero energy so curve starts at 0,0
- no max energy for a molecule so curve gets close but not touch or cross energy axis.
**Only molecules with a greater energy than Ea are able to react **
How does temp affect rate of reaction and how is it shown on Boltzmann distribution?
Temp increases, KE increases so more frequent successful collisions and more molecules can exceed Ea.
When temp increases, all particles energy increases causing Boltzmann distribution to flatten and shift right. The number of molecules doesn’t change so area under curve stays same.
