Rate and Extent of Chemical Change Flashcards
(27 cards)
How can the mean rate of a reaction be calculated?
Change in reactants/time OR Change in products/time
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
How can you measure the quantity of a reactant or product?
In grams or cm³
What are the two possible units for rate of reaction?
g/s or cm³/s (s = seconds)
How could you measure the rate of 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 of reactants in a solution, pressure of gases
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
Explain why increasing the concentration increases the rate of a reaction?
More concentrated means there are more particles in the solution, therefore there are more frequent collisions between reactants
Explain why increasing the pressure of a gas increases the rate of a reaction?
Less space for the particles to move around in, so there are more frequent collisions
Explain why increasing the temperature increases the rate of a reaction?
It increases the speed at which particles move therefore more frequent collisions occur. It increases the number of particles which have the activation energy therefore more collisions result in a reaction
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
What is a catalyst?
Something that increases 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 chemical reaction where the products can react to produce the original reactants
What is the symbol for a reversible reaction?
⇌
If a reaction if endothermic in one direction, what will the reverse reaction be?
Exothermic - it will release the same amount of energy as the endothermic reaction absorbed
Write a word equation for the reversible reaction between hydrated and anhydrous copper sulfate
Hydrated copper sulfate ⇌ Anhydrous copper sulfate + water
What is equilibrium?
A reversible reaction where the forward and reverse reactions occur at exactly the same rate
What is Le Chatelier’s principle?
Predicting how a change in temperature, concentration, or pressure will effect the equilibrium of a reversible reaction
If the concentration of the reactants is increased in a reversible reaction, what happens?
The reaction is no longer at equilibrium, so the forward reaction will increase until the concentration of reactants and products reaches equilibrium again
If the concentration of the products is increased in a reversible reaction, what happens?
The reaction is no longer at equilibrium, so the reverse reaction will increase until the concentration of reactants and products reaches equilibrium again
If the concentration of the products is decreased in a reversible reaction, what happens?
The reaction is no longer at equilibrium, so the forward reaction will increase until the concentration of reactants and products reaches equilibrium again
