Rates of Reaction Flashcards
What is a rate of reaction?
A measure of how quickly a reactant is used up, or a product is formed.
What unit do you measure rate in?
g/s (mass) or cm3/s (volume)
How does the gradient of a line show rate of reaction?
The steeper the line, the quicker the rate of reaction/
Fast reactions finish sooner (plateau).
Ways to increase rate of reaction
Increase temperature
Increase concentration of acid
Increase surface area (using powder instead of lumps)
Use of a catalyst
How does increasing temperature increase the rate of reaction?
Thermal energy transferred to kinetic energy in the particles
Particles move more quickly
Increased frequency of successful particle collisions
Therefore rate of reaction also increases
How does increasing the concentration of acid increase the rate of reaction?
Increased number of particles in a given volume
Increased frequency of successful particle collisions
Therefore rate of reaction also increases
How does increasing the surface area increase the rate of reaction?
Increased number of exposed reactant particles
Increased frequency of successful particle collisions
Therefore rate of reaction also increases
How does the use of a catalyst increase the rate of reaction?
Lowers the required activation energy by providing an alternative reaction pathway
Therefore increasing the rate of reaction
Isn’t used up in the reaction
Ways to measure rate of reaction
Measure volume of gas
Measure mass change
Observe colour change
How do you use gas volume to measure rate of reaction?
Gas syringe
Measure cm3 of gas produced over time
How do you use mass change to measure rate of reaction?
Record the mass of the flask at the beginning of the experiment
Record the mass when it stops decreasing
Equation to calculate rate of reaction:
rate of reaction = 1/change in time
How do you use colour change to measure rate of reaction between sodium thiosulphate and hydrochloric acid?
Put a piece of paper with a black cross under the flask
Start timer and reaction
Record the time when cross is no longer visible
Symbol equation for reaction between marble chips and hydrochloric acid:
CaCO3(s) + 2HCl -> CaCl2(aq) + CO2(g) + H2O(l)
Oxidation
Metal gains oxygen
Loses electrons
