Rates and extent of chemical change Flashcards
What is the rate of a chemical reaction?
how fast the reactants are changed into products
How can you find the speed of a reaction?
recording amount of products formed or amount of reactants used up over time
What factors affect the rate of reaction?
concentration
temperature
surface area
catalyst
How does an increase in temperature increase the rate of reaction?
increased temperature causes particles to move faster
the faster they move, the more frequently they will collide
the faster they move, the more energy they have meaning more of the collisions will have enough energy to make the reaction happen
How does an increase in concentration or pressure increase the rate of reaction?
the more concentrated a solution is, the more particles there will be in the same volume of solvent
this makes collisions more frequent
How does an increase in surface area increase the rate of reaction?
if one of the reactants is a solid, it can be broken up into smaller pieces to increase its surface area to volume ratio
for the same volume of solid, the particles around it will have a larger area to work on so there will be more frequent successful collisions
How does using a catalyst increase the rate of reaction?
a catalyst speeds up the reaction without getting used up, so it is not part of the equation
different catalysts are used for different reactions
all catalysts work by decreasing the activation energy needed for the reaction to occur by providing an alternative reaction pathway
rate of reaction =
amount of reactant used or amount of product formed / time
What practicals can be done to measure the rate of reaction?
measuring the time it takes for:
- precipitation and colour change
- change in mass (with gases) using balance scales
- volume of gas given off using gas syringe
What is a reversible reaction?
a reaction where the products can react to form the reactants again
What is equilibrium?
equilibrium is reached when a reversible reaction occurs in a closed system and when the forward and reverse reactions occur at exactly the same rate.
Give an example of a reversible reaction
hydrated copper sulfate ⇌ anhydrous copper sulfate + water
(hydrated copper sulfate - blue crystals)
(unhydrated copper sulfate - white powder)
What is Le Chatelier’s Principle?
idea that if you change the conditions of a reversible reaction at equilibrium, the system will counteract that change
What happens to the amount of products if temperature is decreased according to Le Chatelier’s Principle?
equilibrium will move in exothermic direaction to produce more heat
more products for exo direction and less products for endo direction
What happens to the amount of products if temperature is increased according to Le Chatelier’s Principle?
equilibrium will move in endothermic direction to try to decrease the temperature
more products for endo direction and less products for exo direction
