Define the term rate of reaction
Rate- a measure of the speed at which products are formed
Rate is modeled by the equation ΔP = _ ΔR . When R à P
Δt Δt
Numeric value is dependent on the coefficient
Ex. 1MnO4-(aq) + 8 H+(aq) + 5Fe2+(aq) à Mn2+(aq) + 4H2O (l) + 5Fe3+(aq)‑
Rate MnO4 à Fe3+ = ΔMnO4- = 1/5 ΔFe3+
Δ t Δ t
(What this means is that Fe3+ will be produced in 1/5th of the time that MnO4- is used up)
Over time, rate of reaction decreases because the reagents are being used up. Rate is inversely proportional to time
Describe suitable experimental procedures for measuring the rate of reactions
Rate equals Concentration divided by time
Rate is measured as the change in product concentration overtime
Experimental techniques used to measure rate include:
- Change in mass
- Volume of gas produced
- Color change
- Light absorption
- Electrical conductivity
Analyze data from rate experiment
Note: This objective mostly tests your ability to analyze concentration over time, mass over time, and volume over time graphs. This is pretty self-explanatory. The only thing to really remember is that the c/m/v of the products increases, and of the reactants decreases. Later objectives will reinforce these ideas
Describe the kinetic theory in terms of the movement of particles whose average energy is proportional to temperature in kelvins
Kinetic Energy- Energy of motion, which is present as particles are always vibrating
The amount of energy in each particle is different, because each gains a different amount of kinetic energy
The average amount of energy in a system is the temperature
Define activation energy
Activation Energy (Ea)- Minimum amount of energy that must enter a system in order to overcome the bonds and start the reaction
Describe the collision theory
Something increases the rate of reaction if it increases the number of collisions between particles or increases the number of particles that have surpassed activation energy.
Increasing collision frequency raises the probability that a particle with enough kinetic energy will cause a reaction to occur
Increasing the energy of the particles makes them more energized and more likely to cause a reaction if collision occurs
Steric factor- The factor which states that in order for a reaction to occur, a collision must occur at a specific geometrical alignment so that the reactive parts of the molecules come into contact
Predict and explain, using the collision theory, the qualitative effects of particle size, temperature, concentration, and pressure on the rate of reaction
Concentration/pressure increases rate of reaction because by increasing the number of particles present (or by forcing them into a smaller space) it increases the likelihood two molecules will collide
Surface area increases rate of reaction because more area increases the chance of collision
Temperature increases rate of reaction because as temperature increases, more molecules achieve Ea and can commence a reaction.
Sketch and explain qualitatively, the Maxwell-Boltzmann energy distribution curve for a fixed amount of gas at different temperatures and the consequences for a change in reaction rate
http://jcsu.jesus.cam.ac.uk/~rpc25/notes/chemistry/kinetics/boltzman.gif
(I don’t know how to post images yet, so bear with me)
The Maxwell-Boltzmann Diagram shows the distribution of particles (y-axis) that have varying amounts of energy (x-axis).
The are under the curve is always the same because the number of particles is the same in both reactions, regardless of temperature
At the lower temperature T1 most particles have yet to reach activation energy
As temperature increases (T2) the distribution shifts so that more particles surpass activation energy. This is why rate is higher when temperature is higher
Describe the effect of a catalyst on a chemical reaction
Catalysts increase the rate of reaction because they provide an alternative pathway with lower Ea for a reaction to proceed (like a bridge over a river).
Sketch and explain Maxwell-Boltzmann curves for reactions with and without catalysts
http://www.physchem.co.za/OB12-che/Graphics/boltzmann-2.gif
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