Chemical reactions, reversible reactions and equilibrium

what is the difference betweem atoms undergoing physical changes vs chemical changes

• physical changes involve substances changing their state, appearance or density due to changes in arrangement of particles

• chemical changes involve energy exchange and happens when atoms break or make bonds.

What happens in a chemical reaction

• first, particles must collide, and they need to have sufficient energy to do so

• old bonds between reactant particles break

• atoms are free to rearrange

• new bonds between product particles form

what is the difference betweem atoms undergoing physical changes vs chemical changes

• physical changes involve substances changing their state, appearance or density due to changes in arrangement of particles

• chemical changes involve energy exchange and happens when atoms break or make bonds.

What happens in a chemical reaction

• first, particles must collide, and they need to have sufficient energy to do so

• old bonds between reactant particles break

• atoms are free to rearrange

• new bonds between product particles form

What kind of changes are observed to confirm a chemical reaction has occurred?

• colour change

• temperature change

• gas being produced

• a precipitate formed (they are due to a solid when two solutions react)

What is collision theory?

Collision theory states that for particles to react, they must collide with sufficient energy to overcome the activation energy

Define activation energy

The minimum energy required for a reaction to start

Describe the effect on temperature on rate of reaction

increasing temperature will increase the kinetic energy of the particles and particles will therefore move faster. As the particles move faster, they will collide more frequently, speeding the rate of reaction.

Describe the effect on concentration on rate of reaction

• When increasing the concentration of reactants, there are more particles per unit volume and this will cause them to collide more frequently. This will also lead to more product being formed.

What are the three ways of increasing the pressure of a gas, and what will it lead to?

• increasing the number of gas particles but keeping the same volume

• decreasing the volume but keeping the same number of gas particles

• increasing temperature

This will lead to particles colliding more frequently

Describe the effect of catalysts on increasing the rate of reaction

• they speed up the rate of reaction by lowering the activation energy so particles will have collisions that reach the activation energy

What are the key characteristics of equilibrium

• reversible reactions that reach equilibrium only occur in a closed system

• rate of forward reaction is always equal to the rate of backward reaction

• concentration of reactants and products remain constant

What is le chatelier’s principal

If a system is at equilibrium and a change in is made in any of the conditions then the system will respond to the change in reaction

How will a reaction respond to a change in concentration in one of the reactants or products in the reaction

• If a change happened in the concentration of a reactant or product, the reaction is no longer at equilibrium. Therefore, the reaction will conteract the change by changing the concentration for the reaction to be at equilibrium again.

Give an example of how a reaction respond to a change in concentration in one of the reactants or products in the reaction

• if the concentration of the reactants increase, more products will be formed to counteract the change in the reaction and return to equilibrium. The concentration of the reactants will therefore decreased.

• If the concentration of the product decrease, more reactants will react until equilibrium is reached again.

How does a reaction respond to a change in pressure, us the ammonia reaction as an example

• If pressure is increased, the equilibrium moves to the side of the equation that has the least number of gasseous molecules so that the increase in pressure is reduced.

• The yeild of NH3 will increase as the reaction will move to the right side which has the least number of moles of gas

• an increase will cause it to move to the side with the most moles and vice versa

Describe what happens when a temperature of a reaction at equilibrium changes

use that reaction as an example

• If the temp is increased the equilibrium will always move in the endothermic direction so that the increase in temperature is reduced

• therefore, the yeild of the endothermic reaction increases and the yeild of the exothermic reaction decreases

• then theres the example but its ok we have a brain