chem chap 14 rate of reaction Flashcards
(15 cards)
what must be observed in order to deduce the rate of reaction?
how much product appears/ disappears
physical measuring of substances
- vol of gas produced
- change in mass of reactant/ product
explain the graph of vol of gas over time
- gradient of the graph is steepest at the start of the reaction hence
ROR is fastest at the beginning
vol of co2 produced per unit time is greatest at the beginning - as the reaction progresses
gradient of graph becomes gentler
ROR decreases with time - at ___ mins, graph levels off
co2 is no longer produced and rxn has stopped
___ of gas is produced in total
what happens to the mass of reactants and products in a rxn
mass of reactants decrease
mass of products increase
explain graph of mass of contents over time
- gradient of graph is steepest at start of rxn
ROR is fastest at the beginning - as the rxn progresses the gradient of graph becomes gentler
ROR decreases with time - at ___ mins, gradient approaches 0
mass of reactants has stopped decreasing
rxn mixture has decreased by a total of __
how is the gradient of graph influenced by mass of reactant/ product
products measured -> gradient negative
mass of products increase with time
reactants measured -> gradient positive
mass of reactants decrease with time
what are effective collisions
when a chemical rxn occurs between particles, the collision is said to be an EC
for this to occur -> reactant particles must collide with energy that is more than or equal to activation energy
when both conditions are fulfilled -> EC occurs causing chem rxn
what is activation energy?
least amt of energy that colliding reactant particles must possess in order to react with each other
what is the effect of EC on ROR & factors affecting this
when EC occurs btwn particles -> ROR increases
factors affecting EC
- conc of reactants
- pressure of systems
- particle size of reactants
- temp of rxn mixture
what is the effect of concentration of a solution on ROR
conc of sltn shows no of particles in a given vol
conc of reactants increases, number of particles per unit volume increases
they collide more frequently increasing frequency of EC
hence higher conc increase ROR
explain the graph of mass of contents with varying concs over time
dif gradients show dif initial rxn rates
as dif concs of sltn used
ror decreases with reactant conc
explain effect of pressure ( gases ) on ROR
particle spacing in gases is more than in liquids and solids
at higher temperatures, spacing between particles in a gas decreases
hence an increase in pressure of gaseous reactants results in an increase in ROR
why do the pressure of liquid and solid reactants have insignificant effect on ROR?
when pressure of liquid and solid particles increases , particle spacing barely changes
hence effect of pressure on ROR is insignificant
what is the effect of particle size on ROR
by breaking a large particle into smaller pieces
-> surface area increases even tho mass and total volume remains the same
higher surface area allows for more EC to occur
hence increase in SA of solid reactants increase ROR
explain graph of mass of varying particle sizes over time
- dif gradients show dif initial RORs due to dif particle size of ___
flask A has steeper initial gradient than flask B -> showing that ROR increases w decreasing particle size
- total decrease in mass of reactants is the same for both flasks as mass of LR used is the same for both flasks
what is the effect of temp on ROR
reactant particles have more kinetic energy which makes them move and vibrate faster
increasing frequency of EC
more reactant particles possess energy that is greater than or equal to activation energy
increasinf frequency EC
hence increase in temp -> increase in ROR
