Chapter 5 Flashcards
rate formula
delta concentration (of the reactants or products)/delta time
what is the rate of a chemical reaction?
concentration
the number of particles dissolved in a specific volume
collision theory
atoms ions and molecules must collide to react
describe the beginning, middle and end of a product graph
beginning: The graph is very steep showing that lots of the product is produced per unit of unit- the reaction is fast
middle: The graph is getting less steep showing that the reaction is slowing down
endL: graph becomes horizontal, showing that no more of the product is being produced, the reaction has stooped
describe the beginning, middle and end of the reactant graph
the concentration of the reactant is falling quickly, showing a fast reaction
middle: the graph is getting less steep showing that the reaction is slowing down as the reactant is used up
end: the reactant is used up the reaction has stopped
effect of changing the size of the solid reactants on the product graph
assuming that everything else remains the same as before and only the size of the solid recatants changes:
The graph starts with a much steeper slope, showing a faster reaction
middle: the graph becomes horizontal more quickly, showing that the reaction stops sooner
end: although the reaction is faster, the same mass of product is produced
how does making the solid reactants smaller affect the rate of reaction
reactions between solids and liquids (or solids and gases) are faster if the solids are preset as lots of small bits rather than a few big ones. The more finely divided the solid, the faster the reaction because the surface area in contact with the liquid or gas is much greater
catalytic converter
high surface areas are frequently used to speed up reactions outside the lab. a catalytic converter for a car uses expensive metals like platinum palladium and rhodium coated onto a honeycomb structure in a very thin layer to keep costs down. in the presence of these metals harmful substances like carbon monoxide and nitrogen oxides are converted into relatively harmless carbon dioxide and nitrogen. the high surface area means the reaction is very rapid. this is important because the gases in the exhaust system are only in contact with the catalytic converter for a very short time.
effects of decreasing the conenetration of the acid // solvent on the product graoh
assumiung everyting else is the same, and only the concentration of the reactnt changes and not its volume, there would be a slower reaction at the beginning -the graph would not be as steep and at the end, the total amount of product would be less compared to the reactnat if it were more concentrated
effect of concentration on the rate of reactio
in general terns, if you increase the concentration of the reactants the reaction becomes faster as increasing the concentratuib increases the chances of particles hitting each other
effect if increasing the temperature on the product graoh
assuming that everything else remains the same as before and only the temperature increases:
The graph starts with a much steeper slope, showing a faster reaction
middle: the graph becomes horizontal more quickly, showing that the reaction stops sooner
end: although the reaction is faster, the same mass of product is produced
effects of increasing temperature on the rate of reaction
increasing the temperature means that the particles are moving faster and so hit each other more often this makes the reaction go faster but only accounts of a small part of the increase In rat
not all collisions end in a reaction as many particles just bounce off of each other. n order for a reaction to happen between particles they must collide with a minimum amount of energy called activation energy (ea) and reactants must gain enough energy to overcome the ea barrier. a relatively small increase in temp produces a large increase in he number of collisions that have enough energy for a reaction to occur
a _____ increase in tempearture ___________ the rate of a reaction
10 degrees celcius
doubles
effects of changing the pressure on a reaction
changing the pressureo n a reaction where the reactants are only soldis or liquids makes virtually no difference to the rate of reaction and so the graph does not change in those cases. but increasing the pressure on a reaction involving gaseous reactants speeds the reaction up as increasing the pressure forces the particles closer together and so they are more likely to hit each other.
the pressure of a fixed amount of gas can be increase by squeezing it into a smaller volume
increasing the pressure of a gas is the same as increasing =g the concentration of the gas
