2.2 Rates of Reaction Flashcards
The Rate of Reaction
Is the change in concentration of a reactant or product per unit time
What are the units for the rate of reaction?
moldm-3s-1
Usually rate is the fastest at the … of a reaction
Start
Rate decreases as the reaction proceeds because the … of the … decreases
Concentration
Reactants
Collision Theory
For a reaction between two molecules to occur an effective collision must take place
What is reaction rate a measure of
How frequently effective collisions occur
What are the five factors that effect the rate of reaction?
Concentration (Pressure for gases), Temperature, Particle size, Catalysts, Light
Why does Concentration effect the rate of reaction?
The increased concentration means there is an increased number of molecules in the same volume, So the distance between molecules is reduced so there is an increase in the number of collisions.
Why does Temperature effect the rate of reaction?
Increasing the temperature provides the molecules with more kinetic energy so they will move faster, this means that on collision more molecules will have enough energy to react.
Why does Particle Size effect the rate of reaction?
Increasing the surface area of a solid means there are more surfaces to collide with each other and the molecules will now be closer together so there is an increase in collisions per unit time leading to an increase in reaction rate
How do Catalysts effect the rate of reaction?
A catalyst increases the rate of reaction without itself undergoing a permanent change
How does light effect the rate of reaction?
Some reactions are much more vigorous when carried out in bright light
Activation Energy
Is the minimum energy required to start a reaction by breaking bonds
For Exothermic reactions ΔH is?
Negative
For Endothermic reactions ΔH is?
Positive
ENdothermic
ENters
EXothermic
EXits
For a successful collision to occur what two things must be true?
The orientation must be favourable
The molecules colliding must have enough energy
Catalyst
Is a substance that increases the rate of a chemical reaction without being used up in the process, it increases the rate of reaction by providing an alternative route of lower activation energy.
Short version for catalyst
Reduces the required activation energy in a reaction
Homogeneous Catalyst
Is in the same physical state as the reactants
Heterogeneous Catalyst
Is in a different physical state from the reactants
Name three industry’s Enzymes are used in?
Dairy industry (Rennin)
Brewing industry (Yeast and Amylase)
Washing powders and detergents (Lipase and Protease)
What are the benefits of using Enzymes?
Lower temperatures and pressures can be used.
They do not harm fabrics or food.
They are biodegradable.
They often allow reactions to take place which form pure products with no side reactions.
What are the four ways to measure the rate of chemical reaction?
Change in gas volume (Gas syringe)
Change in pressure (Manometer)
Change in mass (Weighing Scales)
Colorimetry
