Rates of reaction & Energy changes Flashcards
How does surface area effect rate (marble chip practical)
Smaller chips = larger surface area = faster rate of reaction
How does increasing the concentration of hydrochloric acid effect rate (marble practical)
Grater concentration = grater number of particles in a given volume = faster rate
How is rate of reaction determined through reactants formed
amount of reactant used / time
How is rate of reaction determined through products formed
amount of product formed / time
How do you measure reactant used
if product is a gas, which will be given off, you can carry out the reaction on a set of weighing scales and measure
how much mass is lost
How do you measure product formed
if product is a gas, you can measure the volume of gas produced in a gas syringe
What is activation energy
the minimum amount of energy required for a chemical reaction to occur
How do reactions occur
When reacting particles collide with enough energy
How can you increase the rate of rection
- temperature
- pressure
- concentration
- surface area
- using a cataylst
How does increasing temperature increase rate of reaction
Increasing temperature = increasing kinetic energy of particles
Collide more frequently and energetically, more likely to reach activation energy
How does increasing pressure increase rate of reaction
Increases the number of particles in a given volume therefore increases frequency of collisions
How does increasing concentration increase rate of reaction
increases the number of particles in a given volume and so increases the frequency of collisions
How does increasing surface area increase rate of reaction
There is a greater chance of particles colliding, increases the frequency of successful collisions therefore increases the rate of reaction
How do you find the rate of reaction graphically
Draw tangents to curves and use the slope of the tangent as a measure of
the rate of reaction
What does the gradient equate to
rate of reaction
What is a catalyst
Substances that speed up chemical reactions without being used up
How do catalysts increase the rate of a reaction in terms of activation energy
Catalysts decrease the activation energy by
providing a different pathway for a chemical reaction allowing for more successful collisions
How are enzymes used in the production of alcoholic drinks
Yeast is the enzyme used in the production of ethanol as it is fermented from
sugars
What kind of reaction is a neutralisation reaction
Exothermic
What kind of reaction is a precipitation reaction
exothermic
What kind of reaction is salts dissolving in water
either exothermic or endothermic
What kind of reaction is a displacement reaction
Either endothermic or exothermic
What is required when these reactions (changes in heat energy) take place in a solution
carry them out in a
polystyrene cup with a lid, and measure the temperature change using a
thermometer
What is an exothermic reaction
transfers energy to the surroundings so the temperature of the surroundings increases
Give examples of exothermic reactions
- combustion
- many oxidation reactions
- neutralisation
What is an endothermic reaction
takes in energy
from the surroundings so the temperature of the surroundings decreases.
Give examples of endothermic reactions
- thermal decomposition
- reaction of citric acid & sodium hydrogen carbonate.
- sport injury packs
What is the process of breaking bonds and why
Endothermic -energy must be suppled to break bonds
What is the process of making bonds and why
Exothermic - energy is released when bonds are formed
What is the overall heat energy change for an exothermic reaction
Energy taken in to break < energy released when formed (overall energy has been released)
What is the overall heat energy change for an endothermic reaction
Energy taken in to break > energy released when formed
(because overall energy has been taken in)
How to calculate the energy change in a reaction given the energies
of bonds
Sum of energy taken in to break bonds – sum of energy released to form bonds =
overall energy change
Why may a reactions energy change be negative
energy out is more than energy in
What is activation energy
minimum amount of energy that particles must
have to react
Describe a reaction profiles for exothermic diagram
The products have less energy than the reactants and energy has been released to the surroundings
Describe a reaction profiles for endothermic diagram
reactants have less energy than the products because the energy has been taken in from surroundings
