Rates and Energy Flashcards
What two equations can be used to work out the rate of reaction?
Amount of reactant used ÷ time
Amount of product formed ÷ time
How can the average rate of reaction be found?
By measuring the time it takes for a certain amount of solid to appear in a solution
By measuring the amount of time it takes to collect a certain amount of gas
How can the rate of reaction at any given time be found?
From the gradient of the line on a graph of amount of product against time
What is the relationship between rate and time?
Rate is inversely proportional to time
How could a graph showing the rate of reaction be produced?
By measuring…
- Mass/volume of gas produced
- Changes in colour
- Change in concentration
- Change in pH
…over time
What is collision theory?
Chemical reactions can only happen if particles collide with sufficient energy
What is activation energy?
The minimum amount of energy for particles to collide/to start a reaction
What can increase the rate of reaction?
- Temperature
- Concentration of solutions
- Pressure of gases
- Surface areas of solids
- Using a catalyst
Why do powders react faster than large pieces of solid?
- They have a larger surface area
- This means that there are more collsision in the same space of time
- Therefore, the rate of reaction is faster
Why does increasing temperature increase the rate of reaction?
- Increasing the temperature increases the speed of particles
- This means they collide more frequency, increasing the rate of reaction
- It also means they collide with more energy
- This also increases the rate of reaction
Why does a small change in temperature have a large effect on the rate of reaction?
Because it increases both the speed of the collisions and energy of the particles
Why does increasing concentration increase the rate of reaction?
- Particles in a solutions are moving randomly
- If the concentration increases, there are more dissolved in the same volume
- This means the particles are closer together so collide more often
- This therefore increases the rate of reaction, because the frequency of reactions is increased
Why does increasing pressure increase the rate of reaction?
- There are more molecules/particles in the same volume
- This means they collide more frequently
- Therefore the rate of reaction is increased
What happens to a catalyst during a chemical reaction?
Nothing, it is not used up
What do solid catalysts normally have and why?
A large surface area to make them as efficient as possible