Rate and Extent of Chemical Change Flashcards
(19 cards)
What is the formula for mean rate of reaction?
What in terms of particles increases rate or reaction?
More successful collisions. Factors that increase the number of collisions, or increase the amount of energy with which particles collide will increase rate
How does increasing temperature increase the rate of reaction?
When temperature is increased, the particles have more kinetic energy, so they move faster. This means they collide more frequently and more of the collisions will have enough energy to make the reaction happen
How does increasing concentration or pressure increase the rate?
If a solution is more concentrated, more reactant particles are there in the same volume of solvent. When the pressure of a gas increases, the same number of particles occupy a smaller space. This means collisions between reactant particles are more frequent
How does increasing surface area increase rate?
Breaking up a solid intro smaller pieces increases its surface area to volume ratio. This means that for the same volume, other reactant particles have more area with which to react, so there will be more frequent collisions
How does using a catalyst increase the rate?
They work by decreasing the activation energy needed for the reaction to occur by providing an alternative reaction pathway with a lower activation energy. This means at a given conc, temp etc., a catalyst causes more reactant particles to have enough energy to successfully collide and react
What is an example of a slow/fast chemical reaction?
Slow = rusting of iron
Fast = burning, explosions
Describe collision energy
According to this theory, chemical reactions can occur only when reacting particles collide with each other and with sufficient energy. The minimum amount of energy that particles must have to react is called the activation energy.
What are reversible reactions?
In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions
In reversible reaction, what is true about the reactions in either direction in terms of energy changes?
If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction. The same amount of energy is transferred in each case.
When is equilibrium reached?
When a reversible reaction occurs in a closed system and the forward and reverse reactions occur at exactly the same rate
The relative amounts of all the reactants and products at equilibrium depend on what?
The conditions of the reaction - if a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.
What can the effects of changing conditions on a system at equilibrium be predicted using?
Le Chatelier’s Principle
If the concentration of a reactant in a system at equilibrium is increased, what happens?
More products will be formed until equilibrium is reached again - equilibrium shifts to the right, or the forwards reaction (TO USE UP THE EXTRA REACTANTS)
If the concentration of a product in a system at equilibrium is decreased, what happens?
More products will be formed until equilibrium is reached again - equilibrium shifts to the right, or the forwards reaction (TO REPLACE THE LOSS OF PRODUCT)
If the temperature of a system at equilibrium is increased, what happens?
The system favours the endothermic direction. This means that if the forwards reaction is endothermic, more products are made, and if it is exothermic more reactant is made (less products)
If the temperature of a system at equilibrium is decreased, what happens?
The system favours the exothermic direction. This means that if the forwards reaction is exothermic, more products are made, and if it is exothermic more reactant is made (less products)
For gaseous reactions at equilibrium what does an increase in pressure cause?
The equilibrium positions shifts to the side with the smaller number of molecules as shown by the symbol equation for that reaction
For gaseous reactions at equilibrium what does an decrease in pressure cause?
The equilibrium positions shifts to the side with the larger number of molecules as shown by the symbol equation for that reaction.