rates of reaction + energy chnages Flashcards
What are practical methods for determining the rate of a given reaction
- precipitation reaction
Mix two see through solutions until the mark is gone - change in mass
- volume of gas given off
Use a gas syringe
How do reactions occur when particles collide
When particles collide more and more often the reaction will happen quicker
How does temperature increase rate of reaction
The particles move faster when temperatures are increased - more collisions
Increase the energy of collisions
How does concentration increase rate of reaction
If a solution has a higher concentration then more collisions will happen so rate increases
In a gas increasing pressure means the particles are more crowded and frequency of collisions between particles will increase
How does surface area affect rate of reaction
If one reactant is a solid, breaking it into smaller pieces will increase its surface area to volume ratio and increase collisions of particles
What is a catalyst
A substance that speeds up the rate of a reaction without altering products of the reaction, being its self unchanged chemically and in mass at the end of the reaction
How does a catalyst increase rate of reaction in terms of activation energy
They decrease the activation energy (minimum energy needed for a particle to collide)
They produce a alternative reaction pathway that has a lower activation energy
As a result more of the particles have at least the minimum amount of energy needed for a reaction to occur
What are enzymes and what are used for
Biological catalysts and used in production of alcoholic drinks
What does changes in heat energy show
- salts dissolving in water
- neutralisation reactions
- displacement reactions
- precipitation reactions
- temperature changes can be made to reflect the heat changes
What is a exothermic reaction
Heat energy is given out in a reaction
What is an endothermic reaction
Heat energy is taken in a reaction
Is breaking of bonds endo or exo
Endo
Is making bonds endo or exo
Exo
How to determine if overall heat energy change for a reaction is exothermic
If more heat energy is released in forming bonds in the products than is required in breaking bonds in the reactants
How to determine if overall heat energy change for a reaction is endothermic
if less heat energy is released in forming bonds in the products than is required in breaking bonds in the reactants
Explain activation energy using a reaction profile
On a reaction profile it’s the energy difference between the reactants and its highest point on the curve
If the energy input is less than the activation energy there won’t be enough energy to start the reaction- so nothing will happen
