C8 - Rate of Reaction + Reversible reactions
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rate of reaction
-how fast reactant turn into products
Work out rate of reaction
-measure reactants being used up -products formed
Method to measure rate of reaction
-measure starting mass + record as it decreases as gas is lost -measure increasing gas volume (product) in gas syringe -measure decreasing light passing through solution = precipitate appears (product)
mean rate of reaction
quantity of reactant used/time or quantity of product formed/time
Tangent in reaction graphs
-gradient = rate of reaction -steeper gradient = fast reaction
Factors that affect rate
-temp -SA -concentration of solution -pressure of gas -catalysts
collision theory
-when particles of reactants come together -must collide with enough energy to react
activation energy
-minimum energy necessary for particles to react with
How to increase rate in terms of particles
-increase frequency of collisions -increase energy of collisions
Increased SA in rate of reaction
-more substance exposed to surface -faster reaction -increases frequency of collisions between particles
Effect of temp on rate of reaction
-particles have more energy -for more collisions -more chances to react -increases rate and reduces time
Increased proportion of particles with more activation energy is
greater effect on rate than increased frequency of collisions
Effect of concentration on rate of reaction
-increasing = faster reaction -more particles moving in same volume =more collisions
Effect on increasing pressure on rate of reaction
-more collisions -less space for particles to move -increases rate
catalyst
a substance -increases rate of reaction -remains chemically unchanged -does not get used up
Eg of catalysts
-iron to make ammonia -platinum to make nitric acid
physical state of catalysts and why
-powder form -better SA:V -more effective
How do catalysts work
-provide an alternate reaction pathway to product -lower activation energy is needed -higher proportion of reactant particles have sufficient energy to react
Catalysts effect on frequency of collisions
-increases -increases rate
Pros of catalysts
-cheaper than using extremely high temp/pressure -save money -help environment as no burning of fossil fuels -sustainable = only a little is used
poisoned catalysts
-in chemical plants -contaminated -is prevented from working
reversible reaction
products can react to form reactants again
Litmus paper
-complex molecule -Hlit
HLit
-H is for Hydrogen -red -add alkali = blue