Rates of reaction and energy changes

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skylaa

Cards (21)

what is an exothermic reaction
a reaction which gives out energy to the surroundings, usually in the form of heat and usually shown by a rise in temperature of the surroundings
what is an endothermic reaction
a reaction which takes in energy from the surroundings usually in the form of heat and usually shown by a fall in temperature of the surroundings
what is activation energy
the minimum amount of energy needed for bonds to break and a reaction to start
how are heat energy changes measured
by a temperature change
are salts dissolving in water exothermic or endothermic
can be either
are neutralisation reactions exothermic or endothermic reaction
exothermic but ethanoic acid, sodium carbonate
are displacement reactions exothermic or endothermic reaction
either
are precipitation reactions exothermic or endothermic reaction
exothermic
in terms of bonds, what is an exothermic reaction
the energy used to break bonds is greater than the energy released by forming them
in terms of bonds, what is an endothermic reaction
the energy released by forming bonds is greater than the energy used to break them
how to calculate bond energy
overall energy change = energy required to break bonds - energy release by forming bonds
what is the rate of reaction
how quickly a reaction happens
how to calculate rate of reaction
amount of reactant used or amount of product formed / time
how to measure rate of reaction(core practical)
place marble chips and dilute HCl in a beaker
measure the volume of gas produced using gas syringe. Take readings at regular time intervals
plot graph of results
repeat experiment but with marble more crunched up
how can you increase rate of reaction
increase temperature
increase pressure
increasing concentration
increasing surface area
add a catalyst
how does increasing temperature increase the rate of reaction
the kinetic energy of particle increase, meaning they collide more frequently and successfully
how does increasing pressure increase the rate of reaction
it increases the number of particles in a given volume, increasing the frequency of successful collisions
how does increasing concentration increase the rate of reaction
it increase the number of particles in a given volume, increasing the frequency of successful collisions
what is a catalyst
the substances that speed up chemical reactions without being changed or used up during the reaction
how do catalyst increase rate of reaction / decrease activation energy?
it increases the proportion of particles with energy to react leading to more frequent successful collisions
what are examples of catalysts?
enzymes, like yeast which is used in the production of ethanol