C8 - Rates and Equilibrium
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What is the formula for a mean rate of reaction in terms of reactants?
Quantity of reactant used / Time taken
What is the formula for a mean rate of reaction in terms of products?
Quantity of product formed / Time taken
How can you measure the quantity of a reactant or product?
In grams or in cm3
What are the two possible units for rate of reaction?
g/s or cm3/s (where s is seconds)
How could you measure the rate of a reaction at a specific time from a graph?
Draw a tangent to the curve and calculate the gradient
What is “collision theory”?
The theory that chemical reactions only occur when particles collide with sufficient energy
What five factors can affect the rate of reaction?
Temperature surface area of a solid concentration of reactants in solution pressure of gases catalysts
State the effect of increasing the surface area on the rate of a reaction
Increases the rate
Explain why increasing the surface area increases the rate of a reaction
More particles are available to collide resulting in more frequent collisions
State the effect of increasing the concentration on the rate of a reaction
Increases the rate
Explain why increasing the concentration increases the rate of a reaction
More particles in the same volume result in more frequent collisions
State the effect of increasing the pressure on the rate of a reaction
Increases the rate
Explain why increasing the pressure increases the rate of a reaction
Higher pressure means more particles in the same volume resulting in more frequent collisions
State the effect of increasing the temperature on the rate of reaction
Increases
What is the activation energy?
The amount of energy a particle needs before it will be able to react when it collides with another particle
Explain why increasing the temperature increases the rate of reaction
Increases particle speed for more collisions; more particles have activation energy for successful reactions
What is a catalyst?
Something which speeds up the rate of reaction but is not used up in that reaction
How do catalysts speed up the rate of reaction?
They provide an alternative reaction path with lower activation energy
What is a reversible reaction?
A reaction that can go from reactants to products and from products to reactants
What chemical symbol represents a reversible reaction?
⇌
If a reaction is exothermic in the forward direction what will it be in the reverse direction?
Endothermic
What is dynamic equilibrium?
The point in a reversible reaction when the forward and reverse reactions occur at the same rate
How does the amount of a reactant change at equilibrium?
It doesn’t change
How does the amount of a product change at equilibrium?
It doesn’t change