rate and extent of chemical reactions Flashcards
what is the axis of rate of reaction graphs
amount of product formed against time
how would the quickest reactions look on a RoR graph
steeper line (steeper = faster)
become flat in least time (reactants used up faster)
what is collision theory and what factors increase RoR
chemical reactions can only take place when particles collide with sufficient energy
- frequency & energy (of collisions)
4 factors that affect RoR
temperature
concentration/pressure
surface area
catalyst
gow to find rate of reaction at a point on a graph
tangent, change in y/change in x
how does concentration/pressure affect RoR
and how would it look on a graph
higher (concentration in liquid/pressure in gas) - more particles - more collisions
steeper line, more product
affect of concentration visual change on RoR practical and its challenges
• measuring cylinder: 10cm^3 sodium thiosulfate, put in conical flask
• place flask on paper with black cross
• measuring cylinder: 10cm^3 hydrochloric acid, put in the flask
• swirl solution and start stopwatch
• sulfur is one of the products of ST and HA. it is a solid, causes solution to go turbid (cloudy)
• stop clock when cross cannot be seen from the top
• repeat with 3x for mean, repeat with smaller amounts of sodium thiosulfate
• plot graph
subjective results - disagreement of when mark disappears
measuring RoR using gas practical and challenge
• measuring cylinder: 50cm^3 HCl into conical flask
• attach gas syringe
• add 3cm strip of Mg & start stopwatch
• hydrogen is a product of Mg + HCl, and it is a gas
• measure volume of gas in cylinder every 10 seconds, until no more hydrogen is given off
• repeat with different HCl concs
• plot graph
bubbles may be too vigorous and blow plunger out
how does surface area affect RoR
breaking up a reactant that is a solid will increase SA : Vol ratio
more area to react, rate increases
measuring RoR using mass and challenge
record change in mass as CO2 released every 10 seconds
releases CO2 gas into room
how does temperature affect RoR
increasing temp increases the energy of particles, meaning they move faster.
collision frequency increases & particles have sufficient energy required to collide successfully
how does a catalyst increase RoR
catalysts provide alternate pathway with lower activation energy for the reaction
less energy required for reactions yo take place, RoR increases
what is a reversible reaction and how are the weird equations different
reactants form produce and products can form reactants
how could you change direction of reversible reactions
heating/cooling
energy rules in reversible reactions with example
- if endo in one direction, exo in other
- energy in endo is equal to exo energy
hydrated cooper sulfate -> heated (endothermic) -> anhydrous copper sulfate + water
anydrous copper sulfate + water -> heat energy released (exothermic) -> hydrated copper sulfate
what is equilibrium
the point when forward and backward reaction occurs at exact same time in a closed system
what is le chateliers principle
if the conditions of an reversible reaction change, the reaction responds to counteract change
how do reactions in equilibrium counteract changes in concentration
- increase in reactant, more product will be formed until equilibrium reached
- decrease in product, more reactant will react until enough product for equilibrium to be reached
how do reactions in equilibrium counteract changes in temperature
increase in temp: equilibrium shifts to endothermic direction to try and decrease it. more products on endothermic side
decrease in temp: equilibrium shifts to exothermic direction to try and increase it. more products on exothermic side
how do reactions in equilibrium counteract changes in pressure
increase in pressure: equilibrium shifts to side with fewer molecules, more products on this side
decrease in pressure: equilibrium shifts to side with more molecules, more products on this side
