The Rate and Extent of Chemical Change Flashcards
What is the rate of a chemical reaction?
It is how fast the reactants are changed into products.
What is one of the slowest chemical reactions?
Rusting of iron
What is a slow chemical reaction?
Chemical weathering
What is a moderately-sped chemical reaction?
Magnesium reacting with acid to produce effervescence
What is a fast reaction?
Burning but explosions are even faster and release a lot of gas. Explosive reactions are over within a fraction of a second.
How can you find the speed of a reaction?
By recording the amount of product formed or the amount of reactant sued up over time. The steeper a line is on a graph the faster the rate of reaction. Over time the line becomes less steep as the reactants are used up.
What is collision theory?
The rate of a chemical reaction depends on:
1) The collision frequency of reacting particles. The more collisions there are, the faster the reaction is.
2) The energy transferred during a collision. Particles have to collide with enough energy for the collision to be successful.
What is the minimum amount of energy that particles need to react? Why?
The activation energy - particles need this much energy to break bonds in the reactants and start the reaction.
What do the factors that increase the number of collisions or the amount of energy particles collide with do what?
Increase the rate of the reaction.
What does the rate of reaction depend on?
1) Temperature
2) The concentration of a solution or the pressure of gas
3) Surface area
4) The presence of a catalyst
How does temperature increase the rate of reaction?
When the temperature is increased, the particles move faster. This means the particles will collide more frequently. The faster they move the more energy they have, so more of the collisions will have enough energy to make the reaction happen.
How does the concentration of pressure increase the rate of reaction?
If a solution is made more concentrated, this means that there are more particles knocking about the same volume of water. Similarly, if the pressure of gas is increased, it means that the same number of particles occupies a smaller space. This makes collisions between the reactant particles more frequent.
How does the surface area increase the rate of reaction?
If one of the reactants is a solid, then breaking it up into smaller pieces will increase its surface area to volume ratio. This means that for the same volume of the solid, the particles around it will have more area to work on so there will be collisions more frequently.
How does a catalyst increase the rate of reaction?
A catalyst is a substance that speeds up a reaction without being used up in the reaction itself. This means it’s not apart of the overall reaction equation. Different catalysts are needed for different reactions, but they all work by decreasing the activation energy needed for the reaction to occur. They do this by providing an alternative reaction pathway with a lower activation energy.
