Chemistry 6 - The rate and extent of chemical change

How can we measure the rate of a reaction?

The rate of a reaction can be found by measuring the quantity used or the quantity of product formed over time.

How do you find the rate of reaction graphically?

• Draw tangents to the curve and use the slope of the tangent.

• Calculate the gradient of the tangent to measure rate of reaction at a specific time.

What are the factors that affect the rates of a chemical reaction?

• Temperature

• Concentration of reactants in solutions

• Presence of catalysts

• Pressure of reacting gases

• Surface area of solid reactants

What is the collision theory?

Chemical reactions can only occur when reacting particles collide with each other and with sufficient energy.

What’s activation energy?

The minimum amount of energy required for particles to react.

How does concentration affect the rate of reaction in terms of collision theory?

When the concentration increases, there are more reactant particles to collide so they will collide more frequently, increasing the rate of reaction

How does temperature affect the rate of reaction in terms of collision theory?

When the temperature increases, the reactant particles kinetic energy increases so they move faster and hit each other with more energy, increasing the rate of reaction.

How does pressure affect the rate of reaction in terms of collision theory?

If the pressure is increased, there are more reactant particles in a given volume, therefore there will be more collisions increasing the rate of reaction.

How does the surface area of solid reactants affect the rate of chemical reactions?

Increasing the surface area will increase the amount of particles exposed to the other reactants, leading to more collisions and increasing the rate of reaction.

How does the presence of catalysts affect the rate of chemical reactions?

What are catalysts?

• Catalysts change the rate of chemical reactions

• They aren’t used up.

• Different reactions need different catalysts.

• Enzymes act as catalysts in biological catalysts

How do catalysts increase the rate of reaction?

Catalysts increase the rate of reaction by providing a different pathway for the reaction

What are reversible reactions?

When the products can react to produce the original reactants.

How can the direction of reversible reactions be changed?

By changing the conditions.

How does energy change in reversible reactions?

• The same amount of energy is transferred each way in a reversible reaction (energy will be lost on one side but the other side will gain the same amount back).

• This means that when a reaction is exothermic one way, it will be endothermic the other way.

How does a reaction reach equilibrium?

When the forward and reverse reactions occur at the exact same rate, in a closed system.