S5 - Unit 3 Flashcards
What do industrial processes aim to do?
Maximise profit, minimise environmental impact
How do you make a standard solution?
- Weigh the solid into a small, clean beaker
- Dissolve in a small volume of water
- Transfer to a volumetric flask
- Make it up to the graduation mark with water
- Insert a stopper and invert several times to mix
What is a limiting reactant?
The reactant used up in a reaction which determines the mass of product formed
What is percentage yield?
The amount of product you actually make as a percentage of the amount you should theoretically make
What is atom economy?
A measure of the percentage of reactants that become useful products
Why must reaction rates be controlled in industrial processes?
Because if reaction rates are too high there will be the risk of explosion and if they’re too low the process will not be economical
What factors affect the rate of reaction?
- Concentration
- Particle size
- Temperature
- Pressure
- Collision geometry
What does it mean if a reaction is at equilibrium?
The rate of the forward reaction is equal to the reverse reaction
What happens when equilibrium is reached?
The concentrations of products and reactants remain constant
What factors affect the position of equilibrium?
- Concentration
- Particle size
- Temperature
What do catalysts do to the equilibrium?
Nothing, they only help reach equilibrium faster
What will happen when there is an increase in pressure when a reaction is in a state of equilibrium?
Will favour the side with the least gas moles
What will happen when there is an increase in temperature when a reaction is in a state of equilibrium?
Will favour the endothermic side
What will happen when there is an increase in a certain element when a reaction is in a state of equilibrium?
Will favour the side with the smaller volume of that element
What will happen when there is a decrease in pressure when a reaction is in a state of equilibrium?
Will favour the side with more gas moles
What will happen when there is a decrease in temperature when a reaction is in a state of equilibrium?
Will favour the exothermic side
What will happen when there is a decrease in a certain element when a reaction is in a state of equilibrium?
Will favour the side with the larger volume of that element
What will happen when an alkali is added to an equilibrium reaction?
The H ions will be removed
What will happen when an acid is added to an equilibrium reaction?
The H ions will increase
What must happen before products can be formed?
Reactant molecules must collide in the correct way
What do the collisions of reactant molecules provide?
The energy needed to break the bonds between them and the energy needed to form the bonds on the new products
What factors must be present at the same time for a reaction to be successful?
- Sufficient energy
- Correct geometry
What is activation energy?
The minimum kinetic energy required for a reaction to occur
What type of reaction has taken place in the diagram?
Exothermic
What type of reaction has taken place in the diagram?
Endothermic
What are the blanked out words?
What are the blanked out words?
What is the enthalpy of combustion?
The heat energy given out when 1 mole of fuel burns completely in oxygen
What is the enthalpy of solution?
The energy change when 1 mole of a substance dissolves completely in water
What is enthalpy of neutralisation?
The heat energy given out when 1 mole of water is formed in a neutralisation reaction
What does Hess’ law state?
The enthalpy change for a reaction is independent of the route taken
What is the enthalpy of formation?
The energy needed to make 1 mole of a compound from its elements in their standard state
What type of reaction is the breaking of bonds?
Endothermic
What type of reaction is the making of bonds?
Exothermic
What is the symbol that represents an exothermic reaction?
-ΔH
What is the symbol that represents an endothermic reaction?
+ΔH
What is chromatography?
An important analytic technique which allows chemists to separate substances and identify unknown substances
How does chromatography work?
Substances are separated as they travel in a mobile phase which passes through a stationary phase
What are the two phases in paper chromatography?
Stationary; a sheet of chromatography paper
Mobile; water
What is an advantage of thin layer chromatography?
The mobile phase moves more quickly through the stationary phase
What is gas chromatography used for?
To separate complex mixtures
What factor effect retention time?
- polarity
- volatility
- mass of a substance
How do you calculate the enthalpy change for a forward reaction?
Products - reactants
How do you calculate the enthalpy change for a reverse reaction?
Reactants - products
What is an activated complex?
An intermediate state where particles can either form products or go back to particles of the reactants
What do catalysts do to the activation energy?
Lower the activation energy
What are the principles of chemical industry design?
Availability, cost and sustainability of feedstocks
What is considered to be a raw material in the chemical industry?
- fossil fuels
- water
- air
- metal ores
- minerals
What are feedstocks in the chemical industry?
Simple chemicals or mixtures derived from raw materials used in further manufacture
What is considered in the chemical industry?
- what the cost is
- if the feedstocks are sustainable
- if any by-products can be recycled
