Rates Of Reaction (endothermic/exothermic) Flashcards
Endothermic reaction….?
Reaction that takes thermal energy from the surroundings and makes the surroundings colder
Exothermic reactions….?
Reaction that has excess thermal energy and releases it to the surroundings making them hotter
Law of conservation energy…?
Energy cannot be created/destroyed just changed from 1 to another
Examples of exothermic reactions…?
-hand warmers
-thermal decomposition
Exothermic bond energies…?
-energy released from forming bonds greater than that needed to break the bonds
Endothermic reaction bond energies
-energy needed to break bonds is greater than energy released from making them
Equation to find enthalpy change in terms of bond energies
= Sum of bonds broken - sum of bonds made
As temp increases rate of reaction increases because
-rate increases
-because particles move faster
-more particles have energy greater than activation energy
Why does rate of reaction change when when concentration increases?
-reactions occur when particles collide
-increase concentration - more particles in same volume
-so there are more collisions
How to find rate of reaction at time on graph ?
Gradient / tangent
Exothermic reaction
-energy taken in to break the bonds
-energy given out when bonds are made energy given out greater than energy taken in
Ways to measure rate of reaction?
-loss in mass of reactants
-volume of gas produced
-time for solution to become opaque
Collision theory
Chemical reactions can only occur when reacting particles collide with each other with sufficient energy
Concentration increases ?
Faster reaction
More reactants
More frequent collisions
If solid reactants are in smaller pieces
-they have a greater surface area
-increase surface area of solid reactants increase frequency of collisions
-increase rate of reactions
