Rate of reaction
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What is rate of reaction
a measure of how quickly a reactant is used up, or a product is formed
what are the two calculations used to measure rate of reaction
quantity of reactant used / time taken quantity of product formed / time taken
what does the rat of chemical reaction tell you
how fast reactants turn into products
why are reactions initially fast
because we have a large number of reactant molecules, meaning theres a larger number of collisions per second
what is a successful collision
A collision that produces a reaction
what is activation energy
the minimum amount of energy needed for a collision to be successful
what does collision theory state
chemical reactions can only take place when the reacting particles collide with each other. the collisions must have sufficient energy
what is the rate of a chemical reaction determined by
the frequency of successful collisions
what effect does concentration have on rate of reaction
increasing concentration increases the rate of reaction,
why does increasing concentration increase rate of reaction
• because the reactant particles become more crowded as there are more reactant particles in a given volume • the frequency of collisions between reactant particles increases
why does a higher concentration of reactant give you more product
because we started with more reactant molecules
what effect does surface area have on rate of reaction
increasing the surface area increases the rate of reaction
why does increasing surface area have that effect on rate of reaction
because smaller sized blocks of a solid reactant have a greater surface volume to ratio than larger blocks, this means they have more particles on the surface, meaning there are more collisions per second
how to investigate the effect of surface area on ror
• Use same setup and HCL and magnesium practical 2 . Instead of mg, use a marble chip • measure the volume of carbon dioxide gas produced and use it to determine the ror • change the surface area of marble chips
effect of temperature on ror and why
increasing temperature increases the rate of reaction, this is because increasing temperature increases the particle’s energy - because the particles have more energy, they move faster - this increases the frequency of collisions and each collision has more energy - so more particles can overcome the activation energy barrier and collide successfully
what are catalysts
things that increase the rate of chemical reaction without being used up during the reaction
benefits of catalysts
• they allow us to carry out reactions quickly without needing to increase the temperature and this saves money • they can be reused
how do catalysts increase the rate of reaction
they provide a different pathway for the reaction that has a lower activation energy • They lower the activation energy. This means that more particles can successfully collide per second.
why do we not include catalysts in a chemical equation
because they are not used up so they arent a reactant
what is equilibrium
when reactants are placed in a place that stops reactants and products from escaping , and the forward and reverse reactions take place at the same rate
What does Le Chatelier’s principle state
that if a system is at equilibrium, and a change is made to the conditions, then the system responds to counteract this change
what happens in a reaction that is exothermic
temperature if system increases
what happens in a reaction that is endothermic
temperature of system decreases
what happens when temperature is increased in an equilibrium
the equilibrium shifts to whichever reaction is endothermic, as energy is taken in, which will cause the temperature to fall