Topic 5 - Chemical Reactions Flashcards
Is bond breaking an endothermic or exothermic process?
Endothermic
What is needed to break bonds?
Energy
Is bond formation an endothermic or exothermic process?
Exothermic process
What is an endothermic reaction?
Where there is a decrease in temperature in the surroundings and heat energy is taken in. Ie photosynthesis
What is an exothermic reaction?
When there is an increase in temperature in surroundings and heat energy is given out. Ie respiration
Are physical reactions reversible or irreversible?
Reversable
Are chemical reactions reversible or irreversible?
Irreversable
In chemical reactions, do the reactants turn to products, or the products turned to reactants?
reactants turn to products
How to calculate the rate of a reaction?
Rate = amount of reactant used or product formed / time taken
What does BENDOMEX stand for?
B reaking bonds is ENDO thermic
M aking bonds is EX othermic
What are catalysts?
Substances that speed up chemical reactions without being used up in the reaction
Why do people want to speed up a reaction?
To save time / reduce production time
Gain money
What is activation energy
The minimum energy needed to start a reaction.
What is a catalytic converter made out of?
Platinum or another similar metal
What does a catalytic converter do
Converts gases into water vapour and less harmful gases to reduce harmful emissions
What does a catalytic converter have a honeycomb structure
To give the catalyst a larger surface area
What temperature for catalytic converters work best at?
430’C
Is burning fossil fuels exothermic or endothermic?
Exothermic - heat is given out to surroundings
Is photosynthesis exothermic or endothermic?
Endothermic - uses energy from sun to convert water and CO2 into O2 and glucose
How would you measure the temperature during any of these reactions:
Dissolving salts in water
Neutralisation reactions
Displacement reactions
Precipitation reactions
- Take the temperature of the reactants (making sure they’re the same) - Mix them in a polystyrene cup and measure the temperature of the solution at the end of the reaction
- Put cup into beaker of cotton wool to give more insulation and putting a lid on top to stop energy lost by evaporation
What does the rate of a reaction depend on?
Temperature
Surface area of a solid (or size of particles)
Concentration (or pressure for gases)
Catalyst
What is the result of a larger surface area in hydrochloric acid and marble chip reaction?
Larger surface area = more collisions = greater chance of successful collisions = rate of reaction is faster
How does a more concentrated acid affect a hydrochloric acid and marble chip reaction?
There are more reactant particles in the same volume
There is a greater chance of the particles colliding
The rate of reaction increases
If a solid reactant is broken into small pieces or ground into a powder:
Its surface area is increased
More particles are exposed to the other reactants
There is a greater chance of the particles colliding
The rate of reaction increases
If the temperature is increased in hydrochloric and marble chip reactiom
The reactant particles move more quickly
More particles have the activation energy or greater
The particles collide more often, and more of the collisions result in a reaction
The rate of reaction increases
Using a catalyst
Catalysts increase the rate of reaction without being used up.
They do this by lowering the activation energy needed for the particles to start reacting with each other.
Catalysts are important in industry because they reduce costs.
What does a catalytic converters converter do?
Converts harmful gases into water vapour and other less harmful gases to reduce harmful emissions
Why is it important in industry to keep waste products to a minimum
- it costs money to dispose of them properly
- they don’t make any profit / no commercial benefits
- bad for environment
What is the melting point of potassium chloride
800’C
