Topic7: Rates Of Reaction And Energy Changes P2 Flashcards
What is the equation for rate of reaction?
Rate of reaction=
Amount of reactant used or product formed/ time (s)
What units could be used for rate of reaction?
g/s
cm^3/s
mol/s
How can you measure the rate of reaction when a gas is given off?
- Measure time and collect gas in an upside down measuring cylinder in a trough of water or in a gas syringe to measure the volume of gas produced.
- Measure time and the change in mass
How can you measure the rate of reaction when a precipitate is formed?
Put a black cross below a beaker containing one reactant. Time how long it takes for the cross to disappear after the second reactant is added.
Why is using the precipitation method to investigate rate of reaction not very accurate?
It’s subjective so people are likely to disagree over the exact point at which the cross is no longer visible
How can you measure the rate of reaction using a digital balance?
When a gas is produced as this will cause mass to decrease. The experiment can be carried out on a digital balance and the rate of reaction can be calculated by recording the mass at regular time intervals.
What does the term activation energy mean?
The minimum amount of energy required for a reaction to occurs between two reacting particles.
What must happen for a reaction to occur?
Particles must collide at the correct orientation with sufficient energy to react
In terms of particles what two things could happen when the rate of reaction increases
- More frequent successful collisions because the energy of collisions increase
How can the rate of reaction be increased?
- Increase temperature (so more energy)
- Increase the concentration
- Increase the surface area to volume ratio
- Add a catalyst
- Increase the pressure (for gases)
How does the temperature affect the rate of reaction?
Increasing temperature increases the rate of reaction. This is because the reactants have more energy so more particles have energy above the activation energy meaning more frequent successful collisions will occur.
How does increasing the surface area affect the rate of reaction?
Increasing the surface area of reactants increases the rate of reaction. This is because a greater surface area means there are more exposed particles so more frequent successful collisions.
How does a catalyst affect the rate of reaction?
A catalyst increases the rate of reaction. This is because it provides an alternate reaction pathway with a lower activation energy. More particles will have sufficient energy to overcome the activation energy and react so more successful collisions occur in the same time.
How does concentration affect the rate of reaction?
Increasing concentration increases the rate of reaction. This is because there are more reacting particles in the same volume so there are more frequent successful collisions.
How does pressure affect the rate of a gaseous reaction?
Increasing the pressure of a gaseous reaction increases the rate of reaction. This is because there are more reacting particles in the same volume of gas so more frequent successful collisions occur.
