C6 The Rate And Extent Of Chemical Change Flashcards
How much product?
The amount of product is directly proportional to the amount of limiting reactant used
How to measure reaction times?
Loss in mass of reactants over time
Volume of gas produced over time
Time taken for solution to become opaque or coloured
Volumes of gas
Either use a glass gas syringe
Or a measuring cylinder upside down in water
Rate of reaction
Measures how much product is made each second
Mean reaction time equation
Quantity of reactant formed/ time taken
Or
Quantity of product formed/ time taken
Factors affecting rate of reaction
Temperature Concentrations of reactants in solution Pressure Surface area to volume Catalyst
Changing concentrations
sodium thiosulfate and HCl can be used to investigate concentrations.
RP: investigate how changes in concentration affect the rates of reactions by a method involving the production of a gas and a method involving colour change
How is the rate of reaction affected when the concentration of acid is changed
More gas is collected when the concentration is greater
sodium thiosulfate and HCl can be used reacted to find a colour compound and testing concentration
Increasing the rate of reaction
^concentration
^temperature
^pressure of gases
^surface area
Collisions
Chemical reactions take place when reactant particles collide with each other and form new products
Not all collisions are successful, but a reaction takes place when they are successful
Activation energy
Minimum energy required for particles to react successfully
Collision frequency
The number of successful collisions between reactant particles that happen each second. The more successful collisions the father the rate of reaction
Catalyst
A substance that speeds up a reaction Only needed in small amounts Remains unchanged after the reaction Creates a new pathway for reactions( lower activation energy) Specific to one reaction
Reversible reactions
Products of the reaction can react to make the original reactants again
Forward and backward reaction
Exothermic and endothermic reactions
Equilibrium
When the forward and backward reactions occur at exactly the same rate in a closed system
Equilibrium at the left
Concentration of reactants is greater than the con of products
Equilibrium to the right
If con of reactants is less than con of products
Le Chatelier’s principle
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change
Changing concentrations
If the concentration of a reactant is increased, more products will be formed until equilibrium is reached again
If the concentration of a product is decreased, more reactant will react until equilibrium is reached again
Haber process
N2(g) + 3H2(g) = 2NH3(g)
If the temperature of a system at equilibrium is increased:
The relative amount of product at equilibrium increases for an endothermic reaction
The relative amount of product at equilibrium decreases for an exothermic reaction
If the temperature of a system at equilibrium is decreased:
The relative amount of product at equilibrium decreases for an endothermic reaction
The relative amount of product at equilibrium increases for an exothermic reaction
Making ammonia
Forward reaction is exothermic
To increase yield of products the temp needs to be lower
Gaseous reactions at equilibrium
Increased pressure shifts equilibrium to side with the small number of molecules
Decreased pressure shifts equilibrium to the side with the largest number of molecules
