Topic 2- Rates of Reaction, Equilibrium and yield, and managing resources

Steep gradient

Conversion of reactants to products at a rapid rate

Shallow Gradient

Conversion of Reactants to products occurring much slowly

Zero Gradient

Conversion of reactants to products have reached chemical equilibrium.

Slope for a products

• Have a positive slope

• Increasing

Slope of a reactant

• Has a negative slope

• decreasing

• reducing the number of reactants

What is the collision theory

1. All partials must collide

2. All particals must have the correct orientation

3. All particals must have sufficient energy

Successful collisions

• reactants collide in the correct orientation with sufficient energy.

• Products are formed

• Increase frequency in successful collisions per unit time

Unsuccessful collision

• reactants collide in inncore y orientation and or insufficient information.

• No products are formed

• Decrease frequency in successful collisions per unit time

energy in a exothermic reaction

• a net release of energy

• Negative

• Energy of products is less than energy of reactants

• Decrease in heat energy in the system

Energy in a endothermic reaction

• absorption of energy

• Positive

• Energy of products is greater than the energy of reactants

• Increase in heat energy

axis in an energy profile diagram

• vertical axis: enthalpy of system

• Horizontal axis: reaction pathway

What is concentration?

• Number of particles per unit volume

• Solutions are more concentrated when they have a greater amount of particles per unit of volume.

How does concentration affect the rate of reaction?

• increases the number of reacting particles.

• increases number of collisions between reacting particles per unit time

• increases chance of successful collisions happening.

  • still needs activation energy and correct orientation.

What is temperature?

• measure of average kinetic energy (movement) of particles per unit of time

• particles move at higher speeds and collide with greater energy when heat is transferred.

How does Temperature affect the rate of reaction?

• Increasing temperature = increase kinetic energy

• frequency of collisions between particles increases

• amount of reacting particles increases.

• increases chance in successful collisions.

What is pressure?

• measure of amount of force per unit area

• pressure of a gas is increased by reducing the volume of its container.

How does pressure affect the rate of reaction?

• increasing the pressure of a gaseous mixture causes particles to be closer, causing frequent collisions.

• increases number of collisions per unit time.

• increases chance of successful collisions.

What is surface area?

• particles collide on the surface of a solid reactant in a chemical reaction.

• only particles on surface are available to collide and react with each other.

How does Surface area affect the rate of reaction?

• Increases number of surface particles that can react.

• increases frequency of collisions between reacting particles.

What is a catalyst?

• material that increases the rate of chemical reaction without being consumed

  • Homogenous: same state of matter as reactants

  • Heterogenous: Different state as matter as reactants

• optimised to minimise the amount of them required whilst optimising efficiency, keeping costs down.

How do catalysts affect the rate of reaction?

• provide different reaction pathways that required lower activation energy (E_a)

  • Reduces activation energy required.

Enthalpy (H)

• Measure of heat energy within a system at constant pressure and volume.

• change in heat energy is measured at constant pressure in enthalpy change is represented by (ΔH)

What is a system?

Set of substances and energy that is being studied/focuses on

What is a reversible reaction?

• reactants collide to form products (forward reaction) and products collide to form reactants (reverse reaction)

What is a irreversible reaction?

proceed in a single direction from reactants to products

Open system

• Allows energy and matter to be exchanged with surroundings

• container is open

Closed system

• only allows energy to be exchanged with surroundings

• container is sealed.

what is Equilibrium?

dynamic state in which the forward and backward reaction are ongoing. rate of forward reaction and backward reaction is equal in rate of backward reaction.

• In a closed system

• state of dynamic equilibrium is reached

K_c equation

if K_c is greater than 1, goes to the left

if K_c is less than 1, goes to the right

Le Chatelier’s principle

• ang changes that affects positions of an equilibrium causes the equilibrium to shift in such way as to partially oppose the effects of the change

• system will counteract the change in reaction.

• changes so it returns to its nmormal state

Increase concentration of reactant

• LCP: decrease concentration of reactants

• increase concentration of products

• Equilibrium shift to right

Decrease in concentration of the reactant

• LCP: increase concentration of reactants

• increase in reactants

• shifts to left

Increase concentration of products

• LCP: Decreasing the concentration of the product

• increase in reactants

• shits to the left

Decrease in Concentration of the product

• LCP: Increasing the concentration of the products

• Increase in products

• shifts to the right

Equilibrium mixtures are affected by changes in pressure if

1. The reaction mixture contains gases

2. Difference in total number of moles of gaseous reactants and products in reaction mixture

Increase of pressure (via decreasing the volume)

• LCP: Decreasing the pressure by producing less moles of the gas

• Shifts to the side with less moles of gas particles

Decrease of pressure (via increasing the volume)

• LCP: Increasing the pressure by producing more moles of the gas (to fill the remaining volume of space)

• Shifts to the side with more moles of gas particles

Increase in temperature (Endothermic)

• (heat is the reactant)

• LCP: Decrease in temperature

• Shifts to the right

Decrease in temperature (Endothermic)

• (heat is the reactant)

• LCP: Increase in temperature

• Shifts to the left

Increase in temperature (Exothermic)

• (heat is the product)

• LCP: Decrease in temperature

• Shifts to the left

Decrease in temperature (Exothermic)

• (heat is the product)

• LCP: Increase in temperature

• Shifts to the right

Predict the change that occurred in a system, or whether a reaction is exothermic or endothermic, given the effect of the change on the equilibrium position of the system.

• Lower temperatures prefer product formation when there is exothermic equilibria, but lower temperatures also reduce the rate of product formation.

  • The addition of a catalyst can lower the activation energy/temperature

  • Which is required for a reaction leading to increased rate and yield at the lower temperature.

What is Yield?

• amount of the product formed in a chemical reaction

• %yield = Actual yield / Theoretical Yield x 100

Exothermic reactions (yield)

• favour lower temps

• Increase in temp = decrease in yield, but increase in ROR due to kinetic energy, therefore producing less products at a high rate

Endothermic reactions (yield)

• favours higher temperatures

• Increase in temp = increase in Yield, ROR increases (beneficial for industries) = make more money

Explain the impact of increases in temperature and pressure on manufacturing conditions and costs, and on the environment.

• Temperature

• Pressure

• Reactant concentration

• Particle size / surface area

• Catalyst

• Mixing

Temperature

• Raises cost but can increase reaction rate

Pressure

• Raises cost but can increase reaction rate

Reactant Concentration

• Increases reaction rate

Particle Size & Surface Area

• It can increase the rate of reaction

Catalyst

• Preparation and Structure

Mixing

• Increases the rate of reaction

Explain how use of a catalyst may benefit both the manufacturer and the environment. (Environmental impact )

• Advantages: Biodegradable, less pollution

• Limitations: Farming may cause soil degradation, water pollution, and pesticide use

Explain how use of a catalyst may benefit both the manufacturer and the environment. (Sustainability )

• Advantages: Renewable, lower carbon footprint

• Limitations: Large-scale farming can lead to deforestation or loss of biodiversity, large quantities of water required which are often in short supply. Potentially susceptible to climate change.

Explain how use of a catalyst may benefit both the manufacturer and the environment. (Availability)

• Advantages: Can be locally sourced, reducing import deficiency

  Limitations: Seasonal and geographic factors may limit consistent supply. Reduces land availability for food.

Explain how use of a catalyst may benefit both the manufacturer and the environment. (Energy requirements)

• Advantages: lower energy needed for processing

• Limitations: Some extraction and refinement processes remain energy-intensive

Decomposition of hydrogen peroxide