Rate of reaction

What is the rate of a reaction

This is the amount of time taken for a reactant to be used up or how fast a product is made

What are the methods to determine rate of reaction

• mass loss

• Gas collection

• Precipitation

What is the mass loss method for rate

• when a gas is produced it usually escapes from the reaction vessel so the mass decreases

• The mass is measured every few seconds and change in mass is recorded over time as the gas escapes

• The reaction is performed in a conical flask placed on top of a balance to measure mass

What is the gas collection method

• when a gas is produced in a reaction it can be trapped and its volume measured over time by using a gas syringe

What is the precipitation method

Precipitation reactions form a solid precipitate when two clear solutions are mixed together

• the precipitate cloud the reaction mixture so if the flask is placed over a piece of paper with a cross on it the time taken for the cross to disappear can me measured

What factors affect the rate of reaction

• the concentration of reactants or pressure

• Surface area

• Temperature

• Presence of catalyst

What is the collision theory

This states that successful collisions only occur when reactant particles collide and reach activation energy

What is activation energy

The minimum amount of energy needed to have a successful collision

What affects the rate of successful collisions

• number of particles per unit volume

• The frequency of collisions

• The KE of particles

• The activation energy

What are catalyst

These are substances that speed up the rate of reactions without being consumed in the reaction

What do catalyst do

• they lower activation energy

• They provide an alternative pathway for a reaction to occur

What is a reversible reaction

This is a reaction that can occur in the forwards and backwards direction

What is an hydrated salt

These are salts that contain water of crystallization which affects shape and colour

What are anhydrous salts

These are salts that lost their water of crystallization during heating

What is equilibrium

This is when the rate of forward reaction is equal to the rate of the backward reaction

What is le chatelier principle

This states that when a change is made to the conditions of a system at equilibrium the system automatically moves to oppose the change

What factors affect equilibrium

• temperature

• Pressure

• Concentration

How does increase in concentration affect equilibrium

• equilibrium will shift to the right this is to reduce the effect of increasing the concentration of a reactant and this makes more product and increases the yield

What does decrease in concentration do to equilibrium

• the equilibrium will shift to the left and thus makes less product

What does increase in temperature do to equilibrium

The equilibrium will shift in the direction of the endothermic reaction

What does decrease in temperature do to equilibrium

The equilibrium will shift in the direction of the exothermic reaction

What happens to equilibrium when pressure is increased

Equilibrium will move to the reaction that produces the least number of molecules

What happens to equilibrium when pressure is decreased

This will Favour the reaction that produces the greatest number of molecules