Flashcards in Rate and extent of chemical change Deck (24):
What is an example of a slow reaction?
What is an example of a moderate speed reaction?
Magnesium reacting with acid
What is an example of a fast reaction?
How do you interpret a rate of reaction graph?
The steeper the line, the faster the rate of reaction and the reaction becomes less steep as the reactants are used up
What is collision theory?
Particles have to have enough energy for the collision to be successful and the more they collide, the more likely it is to be successful
What is the activation energy?
The minimum amount of energy required in a reaction to break the bonds of the reactants, starting the reaction
What does the rate of reaction depend on?
Temperature, concentration/pressure, surface area and catalysts
What are the optimum conditions for rate and why?
High temperature as the particles have more energy so can move faster, higher pressure/conc as collisions are more frequent, bigger surface area as collisions are more frequent as more space to work on with same no of particles and using a catalyst as it lowers activation energy
How do you work out rate of reaction?
Amount of reactant used or amount of product formed / time
How do you measure the rate of a reaction?
Visual change through colour or precipitate change, change in mass to see gas given ff and the volume of gas given off
How do you find the mean reaction rate from a graph?
Work out overall change in the y-value and divide this by the total time for the while reaction
How do you find the reaction rate at a particular point on a graph?
Draw a tangent at that point and then work out the gradient
How do you do the magnesium and HCl reaction experiment?
Place flask on scale, add HCl, set scale to 0, add magnesium ribbon, plug flask with cotton wool, start stopwatch, record mass at regular intervals
How do you do the disappearing cross experiment?
Add dilute sodium thiosulfate to a flask, put flask on top of cross, ad HCl to flask, start stopwatch, record the time when the cross became unseeable
What is an equilibrium?
A reversible reaction where the forward reaction is going at exactly the same time as the backwards reaction
What happens if the equilibrium lies to the right?
The conc of products is greater than the reactants
What happens if the equilibrium lies to the left?
The conc of the reactants is greater than the products
What does the position of the equilibrium depend on?
Temperature, pressure and conc
What is an endothermic reaction?
Where energy is transferred from the surroundings
What is an exothermic reaction?
Where energy is transferred to the surroundings
What is Le Chatelier's Principle?
The idea that if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract that chnage
What happens if you raise the temperature in an equilibrium?
The equilibrium will move in the endothermic direction to try and decrease it, meaning that you will now get more products for the endothermic reaction and fewer products for the exothermic reaction
What happens if you raise the pressure in an equilibrium?
The equilibrium will try to reduce the pressure and move in the direction where there are more molecules of gas