1.5 Kinetics Flashcards
What is collision theory
Reactions can only occur when collisions take place between particles with sufficient energy and in the right orientation.
What is activation energy
The minimum amount of energy particles must have in order for a reaction to take place.
Why do most collisions not lead to a reaction
Most collisions are between particles that do not have energy greater than or equal to the activation energy.
How do you increase the rate of reaction
- Increasing the temperature.
- Increasing the surface area (solids).
- Increasing the concentration (liquids and gases).
- Increasing the pressure (gases).
How does temperature affect the rate of reaction
Increasing the temperature increases the rate of reaction:
- Particles have more kinetic energy, so there are more particles with energy greater than or equal to the activation energy.
- This increases the frequency of successful collisions which therefore increases the rate of reaction.
How does the surface area of a reacting solid affect the rate of reaction
Increasing the surface area increases the rate of reaction:
- There is more area for reactants to collide.
- This means more particles are colliding, so increases the rate of successful collisions.
- Therefore, the rate of reaction increases.
How does the concentration of a reacting liquid/gas affect the rate of reaction
Increasing the concentration increases the rate of reaction:
- Greater number of particles in the same volume.
- More particles are colliding, so increases the rate of successful collisions.
- Therefore, the rate of reaction increases.
How does the pressure of a reacting gas affect the rate of reaction
Increasing the pressure increases the rate of reaction:
- Greater number of particles in the same volume.
- More particles are colliding, so increases the rate of successful collisions.
- Therefore, the rate of reaction increases.
What is a catalyst
A substance that speeds up the rate of reaction, but is not used up in the process (remains the same after the reaction).
How do catalysts increase the rate of reaction
- They provide an alternative reaction pathway with a lower activation energy.
- This means that more particles have energy greater than or equal to the activation energy, so increases the rate of successful collisions.
What is the equation for the disappearing cross experiment
- Sodium thiosulfate + hydrochloric acid => Sodium chloride + Water + Sulfur dioxide + Sulfur
- Na2S2O3 (aq) + 2HCl (aq) => 2NaCl (aq) + H2O (l) + SO2 (g) + S (s)
How do you find the rate of reaction in this experiment
- Time how long it takes for the solution to go cloudy.
- Use the formula 1/time to calculate the rate.
Why does the solution go cloudy
Sulfur (a solid) is produced which forms a precipitate, making the solution go cloudy.
Describe the method of the disappearing cross experiment.
- Measure 10cm3 of 0.05moldm(-3) sodium thiosulfate using a measuring cylinder, dilute with 40cm3 of water and pour it into a conical flask.
- Measure 10cm3 of hydrochloric/sulfuric acid and pour into a test tube.
- Place the conical flask onto the cross, add in the acid and start the stopwatch. Stop the stopwatch when you can no longer see the cross and record this time.
- Make a water bath by adding hot water to a beaker and topping up with cold until it reaches the temperature needed. Repeat the experiment for 5 different temperatures in total.
- Use a thermometer to measure the start and final temperature of the reaction and record this.
- Plot 1/time (y axis) against the mean temperature (x axis).
What is the independent variable in the experiment
The temperature.
