7.2.2

Deduce the extent of a reaction from the magnitude of the equilibrium constant.


Magnitude- the size or amount

These three reactions do not have any units because the number of moles between the products and the reactants will have no change [(c+d)-(a+b)= 0]

Deduce the extent of the reaction if Kc is

a. Significantly larger than 1

If Kc is significantly larger than 1 (Kc>>1) then the reaction is almost complete

b. Between 0.01 and 100

If Kc is between 0.01 and 100, this means that both products and reactants are present

c. Extremely small

If Kc is smaller than 1 (Kc<<1) the reaction takes a long time to occur (both forward and backward)

7.1.1

Outline the characteristics of chemical and physical systems in a state of equilibrium


Equilibrium- a reaction in which the rate of the forward reaction is equal to the rate of the backward reaction. 
The amount of material in each condition (or state) remains the same but the process of change from one state to the other continues. Solid material continues to dissolve, and material that is in solution continues to crystallize. Dissolution and crystallization are occurring at the same rate. There is a balance between those two opposite reactions, this is dynamic (changes) equilibrium 

Physical Systems (example)
Bromine is placed in a sealed container at room temperature. Due to bromine being highly volatile it turns into gas close to room temperature and therefore forms a gas above the liquid bromine. Some particles will therefore gain more kinetic energy and turn into gas whilst particles that collide with the liquid particles of the bromine will lose kinetic energy and in turn will change state into liquid.


  (Only watch from 0-30 seconds)






Chemical Systems: (example)

The dissociation of hydrogen iodide (HI) and its elements H2 and I2. A purple iodine gas is produced and the tone of the colour purple increases. Although the purple colour stops to increase after waiting for a set amount of time and therefore gives evidence that equilibrium has been reached.

IB practice questions (Kinetics)

Pg 137

1. D When water is produced that means neutralization has occured
2. A
3. D concentration per unit time
4. B
5. C
6. B
7. C

11. Mass of reactants, Volume, pH (1-7)

B Use of Catalyst, Temperature, Concentration

The catalyst provides an alternate path at which the activation energy is lower therefore increasing the amount particles able to react

Temperature increases the kinetic energy that each molecule possesses and therefore they are able many molecules are able to have a higher kinetic energy than the reactions activation energy. Increases collision frequency

Concentration increases the amount of molecules in the reaction and therefore provides more frequent chances of collision with other molecules to react

C1 it would stay the same, because the mixture is already in excess. The HCl is a limiting factor

C2 Stays the same because the temperature only affects the rate of the product created and not the total volume of the carbon dioxide produced. Because the mass of the reactants are the same, the concentration stayed the same

Kintetics test (my mistakes)

Which one of the following factors does not affect the rate of chemical reaction?
-The enthalpy change of the reaction

*Rate of reaction is rate at which the concentration of product increases per volume over a period of time. As the rate of reaction carries on, the rate starts to decrease because the concentration of the limiting reagent decreases as some of it has been used. At the end , the curve is horizontal as there are no more reactants to create a reaction (no concentration) but they are now in forms of the product instead - there is no HCL for the CaCO3 to react. (From test Graph)

Calcium Chloride is an aqueous solution (aq)

Remember that in a table, the number of decimal places should all be the same 
Curved graphs should always be drawn without a ruler


Other factors that decrease the rate of reaction:
Lower temperature
Smaller Surface area

6.2.5-6.2.7

6.2.5 Sketch and explain qualitatively the Maxwell–Boltzman energy distribution curve for a fixed amount of gas at different temperatures and its consequences for changes in reaction rate


This video explains fully the the energy distribution curve.


It is said that the Boltzman distribution shows the distribution of molecular energy in a gas. It also points out the factors that are apparent in the distribution curve

• No molecules at zero energy.
• Few molecules at high energy 
• No maximum energy value

For the reaction to occur, the particles involved need a minimum amount of energy - the Activation energy. If a particle is not in the shaded area, then it will not have the required energy so it will not be able to participate in the reaction. In this sense the peak at the curve shows that there are many particles with few kinetic energy to the activation energy. In different temperatures however for example if the temperature was increased then the curve will more likely be broader and flatter. This means there are now more molecules with sufficient kinetic energy, but this does not change the activation energy, only the frequency. 

6.2.6 Describe the effect of a catalyst on a chemical reaction.
Catalysts will reduce the activation energy by providing an alternative pathway that requires the less energy for the reaction to occur. The use of a catalyst will therefore speed up the rate of reaction while the catalyst (chemically) remains unchanged, it can however change states. These catalysts provide a platform for which the molecules will react or an active site. Although unchanged, with increased temperature the catalyst becomes denatured.


6.2.7 Sketch and explain Maxwell– Boltzmann curves for reactions with and without catalysts.




This is also a video where water catalyzes the reaction:

6.2.4

6.2.4 Predict and explain, using the collision theory, the qualitative effects of particle size, temperature, concentration and pressure on the rate of a reaction

Independent Variable	Time and surface area of Marble chips
Dependent variable	Volume of gas produced from the reaction
Controlled variables	Concentration and volume of hydrochloric acid, volume of water kept at without air bubbles in the turned measuring cylinder and the mass of marble chips. Also keep in mind the room temperature
Explanations	It is expected that with larger surface areas like powder and smaller marble chips that the reaction will be significantly faster because the particles in the hydrochloric acid has a higher chance of coming in contact and colliding with the calcium carbonate. Therefore the prediction is that the higher the surface area the faster the rate of reaction.
Gradient	The gradient in this case indicates the rate of reaction or the speed at which the reaction is taking place (see definition of rate of reaction)
Units of gradient	cm3 per second
Differences in results	In many cases the results do not seem to support the expected prediction as powder and the smaller marble chips were much slower than the medium sized chips. To some extent the beginning of the reaction where the gradient is steepest for all of these reactions seem to fit the general trend.

6.2.2-6.2.3

6.2.2 Define the term activation energy (Ea)

Activation energy is the minimum energy required for a reaction to take place 

6.2.3 Describe the collision theory

Three factors affect the rate of reaction:

1. Collision Frequency- The more likely the chance of particles colliding with each other the faster the rate of reaction 
2. Number of particles with greater kinetic energy than activation energy (E>Ea)- For a reaction to take place, the particles must have enough energy to overcome the activation energy of the reaction. Successful reactions take place when the kinetic energy is greater than than the activation energy. This is so that the particles do not repel each other.
3. Collision geometry or orientation- The collision must occur in the correct geometrical alignment, this means that reactive parts of the molecule have to be arranged specifically in a collision to enable a reaction with another particle. (see picture below)