Unit 3 Flashcards
In the chemical industry how do you reduce costing
Employment
Raw material alternative
Operating conditions
Maximise profit and minimise impact on environment
Reducing pollution- recycle where possible
Process design; availability, sustainability and cost of feedstock
Environmental- minimise waste, avoid production of toxic waste and design biodegradable products (if possible)
Atom economy
Atom economy is a measure of percentage of reactant atoms which are converted into the desired product of a chemical reaction
% atom economy = mass if desired products/
total mass of reactants X 100
Percentage yield
Quantity of desired product
% yield= actual/Theo X 100
Equilibrium
A state of balance in which nothing changes
Rules of equilibrium
- The concentration of reactant and products remain constant
- The concentrations are usually NOT equal
- The reaction has not stopped
Factors that affect the equilibrium
> concentration
temperature
pressure
Concentration
Reactants; increase- right
Decrease-left
Products; increase- left
Decrease- right
Temperature
Exothermic [-]
Increase-left
Decrease-right
Endothermic [+]
Increase- right
Decrease- left
Pressure
GASES ONLY
Increase- moves to the side with less gas
Decrease- moves to the side with more gas
Catalyst in equilibrium
This does not change the position of the equilibrium
However it does speed up the rate of reaction
Exothermic
Products Less energy than reactants
Endothermic
Products More energy than reactants
Equilibrium and Industry
The laws of the equilibrium are used by industrial chemicals to increase the yield of products
Example- Haber process
Reaction conditions;
Catalyst- iron
Temp- 450 degrees (moderate temp)
Pressure- 200 atmospheres (high pressure)
Forward reaction = exothermic
Backwards reaction= endothermic
Enthalpy
The enthalpy of combustion is the energy released to the surroundings when 1 mole of a substance is burned completely in oxygen
Enthalpy = CM🔺T
Bond enthalpy
Break bonds- endothermic [+]
Form bonds- exothermic [-]
Active complex
An intermediate state that is formed during the conversion of reactants into products
Higher the energy level the less stable
Hess’s Law
The overall enthalpy change for any reaction is independent of the route taken
Redox
Metals give away- oxidised ( MAO)
Non- mentals take- reduction (NTR)
Displacement
A metal higher in the electrochemical series will displace a Lowe metal from a solution if its ions
Reducing agent
Donates electrons
As a reducing agent loses electrons it becomes oxidised
Group one are best reducing agents
Lithium
Oxidising agents
Accepts electrons
As oxidising agents gain electrons they become reduced
Group seven are best oxidising agents
Fluorine
Chromatography
Method of separating and analysing a mixture of soluble chemical
Uses of chromatography
To follow the course of a chemical reaction
To identify additives in foods
To identify finger prints at a crime scene
Paper chromatography
Capillary action the solvent moves up the paper
Can move quickly or slowly
Two stages; mobile phase and stationary phase
Rf value
Rf= distance moves by the compound
Distance moved by the solvent
Standard solution
Is a solution containing precisely known concentrations of an element or substance
Evaporation
A solvent can be removed from a solution by heating the solution in an evaporating basin
Filteration
Is used to collect an insoluble solid from a solid/liquid mixture
Methods for collecting gas
Collecting gas over water can be used for gases that are NOT very soluble
An upturned measuring cylinder should be I. Place of the gas jar
The gas syringe can be used for both soluble and insoluble gases: more accurate as you can read scale on syringe. Although limit to how much gas can be collected
Titration
Used to determine quantity or concentration of a reactant
