5.1 - Collision theory

Question 1

How does adding a catalyst increase the RoR?

Answer 1

• A catalyst provides an alternative pathway or mechanism for the reaction that has a lower activation energy.
• A lower activation energy means particles require less kinetic energy to react.
• More particles have the activation energy, leading to an increased number of effective collisions.
• Consequently, adding a catalyst increases the overall rate of reaction.

Question 2

How does increasing temperature increase the rate of reaction?

Answer 2

• Raising the temperature increases the kinetic energy and speed of the particles.
• As the particles move faster, they collide more frequently, resulting in an increased frequency of collisions.
• Additionally, the increased kinetic energy means more particles have the necessary energy to overcome the activation energy, resulting in a greater proportion of effective collisions.
• Therefore, increasing temperature results in an increased reaction rate.

Question 3

How does increasing pressure increase the rate of reaction?

Answer 3

• Raising the pressure forces the gas particles closer together.
• Particles that are closer together will collide more frequently, increasing the number of effective collisions.
• Therefore, increasing the pressure increases the reaction rate.

Question 4

How does increasing the concentration increase the RoR?

Answer 4

• If the concentration of reactants in solution is increased, the particles will on average be closer together.
• Particles that are closer together will collide more frequently, increasing the number of effective collisions.
• Therefore, increasing the concentration increases the reaction rate.

Question 5

How does increasing SA increase the RoR?

Answer 5

• When the exposed surface area of the solid is increased, more particles on the surface are available to collide and react.This leads to a higher frequency of effective collisions between the solid and other reactants.
• For example, crushing a solid into a powder provides more exposed surface.
• Therefore, increasing the surface area of a solid reactant results in an increased reaction rate.

Question 6

5 factors that affect the rate of reaction

Answer 6

1. Surface area (of solids)
2. Concentration (of solutions)
3. Pressure (of gases)
4. Temperature
5. Catalyst

Question 7

What is the activation energy? (what is this necessary for and what will happen if the energy is greater than the activation energy?)

Answer 7

minimum energy required for a collision to be effective. This energy is necessary to break existing bonds in the reactants and initiate the reaction. Particles with kinetic energies greater than or equal to the activation energy will have sufficient energy to react upon collision

Question 8

What does collision theory state?

Answer 8

1. Orientation- The particles must collide in the correct orientation. They need to be facing each other appropriately.
2. Energy- The colliding particles need at least a minimum amount of kinetic energy. This minimum energy is called theactivation energy (Ea).

Question 9

calculating the rate of reaction of reaction at a specific time

Answer 9

Question 10

Calculating the average rate of reaction from this graph:

Answer 10

Question 11

measuring the rate of reaction between Na2S2O3 and HCl

Answer 11

• a yellow precipitate forms (sulphur)
• Measure fixed volumes of sodium thiosulfate and hydrochloric acid solutions.
• Warm the solutions to the desired temperature in separate test tubes.
• Combine the heated solutions in a conical flask.
• Position the flask over a black cross on a piece of paper to observe through the initially clear solutions.
• Record the time it takes from the moment of mixing until the black cross is fully obscured by the yellow sulfur precipitate.
• Repeating the experiment at various temperatures allows for comparison of reaction rates, noting that a quicker obscuration time indicates a faster rate.

Question 12

How to measure reaction rates? (3):

Answer 12

1. Measuring a decrease in mass - observing a decrease in mass over time - gas is released mass decreases etc.
2. measuring the volume of gas given off - use a gas syringe to measure the volume of gas produced over time
3. timing how long a precipitate takes to form - measuring how long it takes for a mark to become obscured by the precipitate - using the same observer and reference mark

Question 13

Reaction rate definition

Answer 13

• the change in conc. of a reactant or product over time
• rate of reaction = the amount of reactant used up or product formed/time