Rates And Energy Flashcards
How can the rate of reaction be found?
Measuring the amount of reactant used, or how much of a product is formed, and the time taken.
Also you can measure the time taken for a certain amount of solid or gas to appear in a solution.
Rate of reaction equation
Rate of reaction = amount of reactant used/time
Or
Rate of reaction = amount of product formed/time
On a graph with product or reactant against time, how can a rate of reaction be found at any given time?
The gradient. The steeper the gradient, the faster the reaction is at that time.
What does the collision theory state?
That reactions can only happen if particles collide. However colliding isn’t enough as there must be enough energy to change into new substances.
What is the minimum energy that it needed for a reactions?
The activation energy
What factors increase the chance of collisions or the energy of the particles?
Temperature Concentration of solutions Pressure of gases Surface area of solids Using a catalyst
Why are smaller pieces with the same mass better than large pieces for a reaction?
Smaller pieces have a larger surface area, more area exposed. This means there will be more collisions in the same time, so the rate of reaction increases?
What happens to a rate of reaction when the temperature is increased?
With an increased temperature the speed of the particles increases because they have gained more kinetic energy. This means they will collide more often and this increases the rate of reaction.
If there was a rise or fall of even 10 degrees C, how much will the rate of reaction increase or decrease?
It will double.
What happens to a rate of reaction if the concentration of a solution increases?
This means there are more particles dissolved in the same volume, which means more collisions. This then increases the rate of reaction.
What happens to a rate of reaction if the pressure of a gas increases?
This means that more gas molecules are out into the same volume so they collide more frequently which increases the rate of reactions.
What is a catalyst?
A substance that changes the speed of a reaction but is not changed itself. It isn’t fully used up so at the end of a reaction, it can be collected and used again.
How do catalysts speed up a reaction?
They lower the activation energy so that more collisions occur.
In what form can catalysts be in to make them more effective?
They are solids that have large surface areas.
Why do different reactions need different catalysts?
Catalysts often work with only one type of reaction.
Why are catalysts used in many industrial processes?
They can be expensive but they can be economical because they can be reused. Also it means that the catalysts reduce the activation energy and time needed for reactions. This means costs and environmental impacts are reduced. It can also conserve resources like fossil fuels.
How can some catalysts cause harm if they get into the environment?
Many of the catalysts used industry involve transition metals and their compound which can be toxic.
What can offer more development of catalysts?
Nanoscience can help find better and more efficient catalysts.
Also enzymes which are biological catalysts cans be used to also reduce energy costs.
What are exothermic reactions?
Reactions that transfer energy to the surroundings.
What are examples of exothermic reactions?
Combustion, such as burning fuels
Oxidation reactions such as respiration
Neutralisation reactions involving acids and bases.
What are endothermic reactions?
Reactions that take in energy from the surroundings.
What is an example of an endothermic reaction?
Thermal decomposition reactions need to be heated continuously to keep the reaction going.
In a reversible reaction if one direction is exothermic, what is the other direction?
Endothermic. It would keep reversing
What is the difference between the energy released in an exothermic reaction and the energy taken in in an endothermic reaction, in a reversible reaction?
There is no difference, they are equal.
