Exo Endo Flashcards
(21 cards)
What is an exothermic reaction
When heat is transfered to the surroundings
Examples of exothermic reactions
Combustion reactions
Many oxidation reactions
Most neutralisation reactions
What is an endothermic reaction
When energy is taken from the surroundings
Examples of endothermic reactions
Thermal decomposition reactions
Reactions of citric acid and sodium hydrogencarbonate
What could ur independent variable be for the required practicle: temp changes in reacting solutions
Concentration of the liquid
Surface area of the solid
Type of alkali/ acid
Type of metal/ metal carbonate
What is a problem with the temperature change in reacting solutions practicle and how can u stop it
Unwanted heat transfer
Use a lid on the beaker to stop it
2 hazards for the required practicle, what can happen and how to stop it
Dilute acids and alkalis,
May irritate skin or eyes,
Wear eye protection and rinse of when touched by it
Solutions of metal salts ,
Dangerous to environment,
Dispose of it as advised by pro
Describe an exothermic reaction graph
Reactants start as a horizontal line near top of graph
When energy is released a line is drawn straight down
Products carry on the horizontal line but futher down
Describe the graph of an endothermic reaction
Reactants start as a horizontal line near bottom of graph
When energy is absorbed draw a vertical line straight upwards
Products carry of horizontal line but futher up
An endothermic reaction uses the process of ________ ______ which means heat is ______ ____
Breaking bonds
Taken in
An exothermic reaction uses the process of _____ _____ which _______ _____ energy
Forming bonds
Gives out
Hiw to calculate an energy change for a reaction using bond energies
Add together all the bond energies for the bonds in the reactants ( energy in)
Add together all the bond energies for the bonds in the products ( energy out)
Energy change = energy in - energy out
Concentration in mol/ dm³ =
Amount of solute in mol ÷ volume in dm³
1 dm³ =
1000 cm³
How to multiply from mol/ dm³ to g/ dm³ and vise versa
Multiply by reletive formula mass
Divide by reletive formula mass
Why use a polystyrene cup in the practicle
Slows heat loss from side and bottom
What do reaction profiles show
Show the progress of the reaction on the x axis and energy level on y axis
How to figure out if a reaction is endo or exo with bond energy
Total bond energy of reactants - total bond energy of products
If overall energy change is
<0 = endo
>0 = exo
What does bond energy measure
Strength on chemical binds
How do catalysts increase the reaction rate
Lowers activation energy
What is activation energy
Minimum amount of energy required for a chemical reaction to occur
