6 Rates H only Flashcards
What is the rate of a chemical reaction in terms of reactants?
How quickly the reactants in a reaction are used up
What is the rate of a chemical reaction in terms of products?
How quickly the products in a reaction are formed
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 reactant 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 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 factors can affect the rate of a reaction?
Temperature, surface area of a solid, concentration or reactants in solution, pressure of gases
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, there are therefore more frequent collisions between reactants.
State the effect of increasing the concentration on the rate of reaction
Increases
Explain why increasing the concentration increases the rate of reaction
More concentrated means more particles in solution, therefore more frequent collisions between reactants.
State the effect on increasing the pressure of a gas on the rate of reaction
Increases
Explain why increasing the pressure of a gas increases the rate of a reaction
Less space for the particles to move around in, therefore 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 the speed at which particles move therefore more frequent collisions. Increases the number of particles which have the activation energy therefore more collisions result in a reaction.
What is a catalyst?
Something which changes the rate of a reaction but is not used up in that reaction
How do catalysts speed up reactions?
They provide another route for the reaction to take place which has a lower activation energy.
What is a reversible reaction?
A reaction which can go from reactants to products but also from products to reactants
What chemical symbol represents a reversible reaction?
one arrow going left on top of an arrow going right
If a reaction is exothermic in the forward direction what will it be in the reverse direction?
Endothermic
Two reactants require 30kJ to turn into products. What energy transfer is involved when the products turn into reactants?
30kJ is released
What is equilibrium?
The point in a reversible reaction when the forward and reverse reactions are occurring at the same rate
How is the amount of reactant changing at equilibrium?
It is not changing
How is the amount of product changing at equilibrium?
It is not changing
What is Le Chatelier’s principle?
When a reaction at equilibrium is changed, it will seek to counteract that change
A reaction is exothermic in the forward direction. What will occur if the temperature is increased?
The backward reaction will increase as it is endothermic and will reduce the temperature
A reaction is at equilibrium when some product is removed. What will occur?
The forward reaction will increase as that will increase the amount of product
The reaction below is at equilibrium. What will occur when the pressure is increased? 2H?(g) + O?(g) ? 2H?O(g)
The forward reaction will increase as there are fewer molecules on the right. This will reduce the total number of molecules and therefore the pressure.
