Chemistry topic 6

What do they mean by rate of chemical reaction

How quickly the reactants are converted into products

Formula for rate

Rate = mass of product produce or lost / time taken

Rate = volume of product produced or lost / time taken

What is precipitation

Measures the time it take for a mark to disappear

What is colour change

Measure the time it takes for a colour change to occur

What are the problems with precipitation and colour change

Can’t plot results on a graph

Its subjective - people might interpret the colour change differently

How do you calculate the rate of a reaction by measuring the change in mass

Use a balance to monitor how the mass change over time

Take measurements at regular intervals

Plot results on a graph

Calculate the gradient

How can you use a gas syringe to measure the rate of a chemical reaction

The gas syringe measures how the volume of gas changes over time

Take measurements at regular intervals

Plot your results on a graph

Calculate the gradient

5 factors that affect the rate of a chemical reaction

Temperature

Concentration

Pressure

Surface area

Catalyst

What happens to the rate of the reaction when the temperature increases (explain what happens to the particles)

Rate of reaction increases

The particles move around faster which makes them collide more frequently

This will make them collide with more energy so the collisions is more likely have endowing energy to react successfully

What happens to the rate of the reaction when concentration or pressure increases (explain what happens to the particles)

Rate of reaction will increase

The number of particles per unit of volume will increase which will make the collision frequency increase

What happens to the rate of the reaction when the surface area of a solid increase (explain what happens to the particles)

Breaking the solid into smaller pieces increases the surface area to volume ratio

With the same volume of solid the particles will have a greater area which they can more frequently collide re

What is the collisions theory

For particles to react the have to collide with sufficient energy and right direction

What is activation energy

Minimum amount of energy that particles requires to react together

Why do particles need activation energy

To break the bonds of the reactants to begin the reaction

How does a catalyst increase the rate of reaction

Lowering the activation energy required for a reaction giving it an alternative route

It requires less energy to react

Why do concentration/time graphs plateau

The reactants are used up

How do you find the gradient of a line

Gradient = change in y / change in x

How do you find the rate of reaction at a particular point on a concentration/time graph

Draw a tangent to the line at that point

Pick 2 points on the line and do the change in y / change in x

The gradient is the rate

What is reversible reaction

A reaction that can go backwards and forwards

What happens to the reactants during the reaction

Concentration of reactants fall which slows down the forward reaction

Concentration of product rises speeding up the backwards reaction

What does equilibrium mean

The rate of forward reaction is equal to the tar of the backward reaction

What does dynamic equilibrium mean

When both forward and backward reaction are happening but there is no overall affect since they are at the same rate

Products is breaking down as quickly as it is being formed

What condition is required for a reaction to reach equilibrium

Closed system

What does it mean if the position of equilibrium lies to the right

The products concentration is greater than the reactants

Factors that change the position of equilibrium

Temperature

Pressure

Concentration of reactiants and products

What is Le Chateliers principle

The system will counter the change in conditions in order to restore equilibrium

Why is Le Chatelier principle useful

It helps us predict the affect of changes made to the system

According to Le Chatelier principle what happens if you decrease the temperature

The position of equilibrium will shift towards the exothermic side to produce more heat

According to Le Chatelier principle what happens if you increase the pressure

The position of equilibrium will shift to the side with less molecules of gases to reduce pressure

According to Le Chatelier principle what happens if you decrease the concentration of the reactants

The position of equilibrium will shift to the left to increase the reactant concentration