2.1 The rate and extent of chemical reactions

What is the rate of reaction?

Amount of reactant used or product formed per unit time

What is the equation for rate of reaction?

Rate = amount of reactant used divided by time

What is an alternative rate equation?

Rate = amount of product formed divided by time

What units can rate of reaction have?

g per second cm3 per second or mol per second

What quantities can be used to measure rate?

Mass volume or moles

How can rate be found from a graph?

By drawing a tangent and finding its gradient

What does the gradient of a tangent represent?

Rate of reaction at a specific time

Name five factors affecting rate of reaction

Concentration Pressure Surface area Temperature Catalysts

What does collision theory state?

Particles must collide with sufficient energy to react

What is activation energy?

Minimum energy needed for a reaction to occur

How does concentration affect rate?

Higher concentration increases collision frequency

How does pressure affect rate?

Higher pressure increases collision frequency in gases

How does surface area affect rate?

Greater surface area increases collisions

How does temperature affect rate?

Higher temperature increases collision frequency and energy

What is a catalyst?

A substance that speeds up a reaction without being used up

Are catalysts included in equations?

No

What do enzymes act as?

Biological catalysts

How do catalysts increase rate?

By lowering activation energy

What do catalysts provide?

An alternative pathway with lower activation energy

What is a reversible reaction?

A reaction where products can turn back into reactants

What symbol represents a reversible reaction?

⇌

Give an example of a reversible reaction

Nitrogen plus hydrogen ⇌ ammonia

If a reaction is endothermic one way what is it the other way?

Exothermic

Is the energy transfer the same in both directions?

Yes

What is equilibrium?

When forward and backward reactions occur at the same rate

What type of system is needed for equilibrium?

A closed system

What does Le Chatelier’s principle state?

System responds to counteract changes

What happens if reactant concentration increases?

Equilibrium shifts towards products

What happens if product concentration increases?

Equilibrium shifts towards reactants

What happens when temperature increases?

Equilibrium shifts in endothermic direction

What happens when temperature decreases?

Equilibrium shifts in exothermic direction

For an exothermic reaction what does increasing temperature do?

Decreases yield

For an exothermic reaction what does decreasing temperature do?

Increases yield

For an endothermic reaction what does increasing temperature do?

Increases yield

For an endothermic reaction what does decreasing temperature do?

Decreases yield

What happens when pressure increases in gases?

Shifts to side with fewer moles of gas

What happens when pressure decreases in gases?

Shifts to side with more moles of gas

In the Haber process which side has fewer moles?

Product side ammonia

What happens to equilibrium if pressure increases in Haber process?

Shifts right to make more ammonia

If a reaction produces more gas what does high pressure do?

Decreases yield

If a reaction produces less gas what does high pressure do?

Increases yield