Paper 2: Rates of reaction Flashcards
How is rate of reaction calculated
Reactant/product used or formed/time
Units for rate of reaction
g/s cm3/s or mol/s
3 ways of meausring rates of reaction
-Loss of mass of reactions
-Volume of gas produced
-Time for a solution to become opaque
Describe measuring rate by measuring mass loss
-Place reaction flask on balance
-A gas is given off, so record the decrease in mass in time intervals
-Plot a graph of mass vs time
Describe measuring rate by monitoring volume of gas
-Connect a gas syringe to a reaction flask and measure volume of gas formed in intervals
-Plot a graph of volume vs time
Describe measuring rate by monitoring the disappearance of a cross
-Take a piece of paper and mark a cross on it. Put reaction flask on this cross. Measure the reagants and measure how long it takes for a cloudy mixture to conceal a cross
How to find rate of reaction and some time from a graph
-Pick a point corresponding to the time, and find the tangent to the curve at this point
-The tangent is the gradient the steeper the tangent the faster the rate
Factors affecting rate of a chemical reaction
-Conc of reactants
-Pressure of gases
-Surface area
-Temperature
-Catalysts
What is collision theory
Chemical reactions can occur only when reacting particles collide with each other with sufficent energy
Effect of increasing temperature on rate of reaction
-Kinetic energy increases
-Particles move faster
-Collide more frequentley/higher chance of collisions
Effect of increasing concentration on rate of reaction
conc increases=faster reaction
more reactants=more frequent collisions
Effect of the increasing pressure of a gas on the rate of reaction
-Increases number of gas molecules so increases frequency of collisions and the rate of reaction
Effect of increasing the surface area on rate of reaction
-A greater surface area increases frequency of collisions and rate of reaction
How does a catalyst affect the reaction profile?
-increases reaction by providing a different pathway for a reaction that has a lower activation energy
-Reaction profile for a catalysed reaction will have a lower maximum of the curve (lower activation energy)
What is a reversible reaction
Reaction can react backwards to produce the original reactants