Rates Of Reaction Flashcards
What can change the rate of reaction?
-surface area
-concentration
-temperature
- use of a catalyst
What does the gradient tell us?
The rate of reaction
What has to happen for a reaction to occur? (Collision theory)
-reactant particles must collide
-must collide with energy >the activation energy
What is a catalyst?
- substance that speeds up the rate of reaction
- doesn’t get used up
-remains chemically unchanged
Explains what happens to the rate of reaction when the temperature is changed
The particles will gain kinetic energy (which will make them move faster) and the collision will be faster per unit time (more frequent)
-more particles collide with energy>activation energy
What will change if you change the pressure in gases?
Number of particles in a given volume
Explain what will happen to the rate of the reaction if the concentration is changed
Means that there are more particles of that reactant in a given volume,more collision between reactant particles per unit time
Explain what will happen to the rate of the reaction if the surface area is changed
Smaller pieces have a bigger surface area, more particles of solid are in contact with other reactant
What is the equation for calculating average rate?
Rate= change in amount of product/time
Rate= change in amount of reactant/time
What is the word equation for the marble chip practical ?
Calcium carbonate + hydrochloric acid=
calcium chloride + carbon dioxide +water
What is the symbol equation for the marble chip practical ?
CaCO3+2HCl=
CaCl2+CO2+H2O
How does a catalyst work?
Provides an alternative pathway with lower activation energy
This means that more collisions will have energy equal to/greater that the activation energy, so more successful collisions
What does collision theory states in order for a reactant to occur?
Reactants must collide with sufficient energy-greater than or equal to the activation energy for the reaction
What is activation energy?
Minimum amount of energy particles must possess if they are to react when they collide
What is rate of reaction measured in?
Number of successful collisions
Referring to the collision theory, why the rate of reaction decreases as the reaction proceeds?
As time goes, reactant particles get used up as there are fewer reactant particles, there are fewer successful collisions per unit time
Less frequent collisions
Why is increasing surface area increases the rate of reaction?
Smaller pieces have a bigger surface area than larger pieces with the same total mass
This means more particles of the solid reactant are in contact with particles of the other reactant
This results more collisions between reactant particles per unit time, so the rate of reaction increases
Why is increasing concentration increases the rate of reaction?
Increasing concentration of a solution means that there are more particles of that reactant in a given volume
As a result there are more collision between reactant particles per unit time, so the rate of reaction increases
Why is increasing pressure of the gaseous reactant increases the rate of reaction?
Increasing the pressure means that there are more reactant particles in a given volume
As a result there are more collisions between reactant particles per unit time, so the rate of reaction increases
Why is increasing temperature increases the rate of reaction?
At higher temperature, reactant particles have more kinetic energy and so move around faster. This results in more collisions per unit time
+more particles will collide with energy equal to/greater than the activation energy, so more successful collisions
What happens to the rate of reaction when a catalyst is present?
Catalyst provide an alternative reaction pathway with a lower activation energy
Which means more collisions will have energy equal to/greater that the activation energy= more successful collisions
