The Rate and Extent of Chemical Change
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What is the rate of chemical reaction?
Rate of a chemical reaction is how fast the reactants are changed into products
How can a rate of reaction be measured?
Rate of reaction = amount of reactant used ÷ time Rate of reaction = amount of product formed ÷ time
What does the rate of a chemical reaction depend on?
• Collision frequency of reacting particles • Energy transferred during collision
Explain how the collision frequency of reacting particles effects the a rate of reaction
More collisions = faster the reactions
Explain how the energy transferred during collision effects the a rate of reaction
Particles have to collide with enough energy for collision to be successful
What is activation energy?
Minimum amount of energy needed for particles to react
What is activation energy used for?
Particles needs this much energy to break the bonds in reactants (at start of reaction)
Name 4 factors that affect the rate of reaction (excluding collision theory)
• Temperature • Concentration of Solution/Pressure of Gas • Surface Area • Catalyst
Explain how increasing the temperature will increase the rate of a reaction
• When temperature is increased = particles move faster • Moving faster = collide more frequently • Faster they move = more energy = so more of collision will have enough energy to make reaction happen
Explain how increasing the concentration/pressure will increase the rate of a reaction
• Solution more concentrated = more particles knocking back in same volume of water (solvent) • Pressure of gas increased = same number of particles occupies smaller space
Explain how increasing the surface area will increase the rate of a reaction
• If one reactant is solid → breaking it up into smaller pieces = increases surface area to volume ratio • Means same volume of solid = particles around it will have more area to work on → more frequent collisions
Explain how increasing using a catalyst will increase the rate of a reaction
• They work by decreasing activation energy needed for reaction to occur 2. They do this by providing an alternative reaction pathway with lower activation energy
What is a catalyst?
Catalyst is a substance that speeds up reaction WITHOUT being used up in reaction itself
What does it mean if a system is in equilibrium?
Forward reaction is going at exactly the same rate as backward one
What is dynamic equilibrium?
Both reactions (forward and backwards) are happening but no overall effect = conc. of reactants + products have reached balance and won’t change
When does equilibrium take place?
If the reversible reaction takes place in closed system
What is a closed system?
Where none of the reactants/products can escape AND nothing can get it in
In reversible reactions, if reaction is endothermic in one direction, the other direction will be…
Exothermic (reversible reactions can be endothermic and exothermic)
The position of equilibrium can be on…
The right or left
When a reaction is at equilibrium does it mean the amount of reactants = amount of products?
NO. When reaction’s at equilibrium it doesn’t mean → amount of reactants = amount of products.
What does it mean if equilibrium lies to the right?
Concentration of product > reactants
What does it mean if equilibrium lies to the left?
Concentration of reactants > products
What conditions affect the position of equilibrium (excluding the reaction itself)?
• Temperature • Pressure (only affects equilibria involving gases) • Concentration of reactants and products
What is Le Chatelier’s Principle?
It’s the idea that if you change the conditions of a reversible reaction at equilibrium → system will try to counteract change