Example: production of chlorine using a membrane cell
Reactants are entering the reaction vessel,
the reaction is taking place and the
products are being removed continuously.
Advantages: More produce can be
made, more economic-running costs
lower due to lower energy
requirements, less environmental
pollution, more time efficient, less
labour (automatic machines)
Disadvantages: very wasteful if it
goes wrong, only one product, high
start up cost
Batch- (cake)
Stages occur at separate times in sequence. After the
reaction is over the vessel is emptied and the process
starts again
Advantages: not very wasteful if goes wrong, low start up cost
Disadvantages: less
produce, more time
consuming
Mercury Cell- large scale method for making chlorine
gradually being phased out, losses of toxic
mercury to the environment, more expensive to
run
chemical manufacture- batch or continuous
most chemical processes involve- feedstock preparation -->reaction-->separation--> products
Feedstock= reactants needed for the chemical process, prepared
from raw materials present in the environment (eg. natural gas, crude
oil, coal, limestone, air, water)
Handling of feedstock is important
gases and liquids can be piped, but solids are
expensive to handle
Co-products= products other than the desired on formed in the reaction.
By-products= produced as a result of unwanted side reactions. do not
appear in reaction equation. conditions can be altered to minimise these
reactions.
the separation stage- produces the pure product, un-reacted feedstock, any co-products, bi- products
un-reacted feedstock is recycled to reactor and increases the efficient of the process. also minimises waste effluent
Cost- research and development, plant design, construction and start up.
Fixed costs, have to be paid no matter how much product
made. eg. cost of construction (capital cost)
Variable costs- depend on level of production. greater production- greater variable costs
eg. raw material, effluent treatment and distribution
Efficiency
energy is expensive- therefore needs to be efficient
exothermic reaction give out heat which by using heat
exchanger can produce hot water/ steam which can be used
When choosing temperature and pressure- some may
go for highest value--> but this is costly to build and
maintain. yield could be affected
Transporting dangerous liquids
Safety procedures: protective clothing+ breathing apparatus, concrete base-
stops soil from absorbing, lead-lined steel for lorry (unreactive-strong incase
of collision/impact), glass-lined steel ( unreactive), pressurised nitrogen tank,
bromine detector, dump tank
Electronic configuration
Rules for filling shells: 1) fill lowest energy orbitals
first (bottom upwards) 2) a maximum of 2 electrons
can occupy any orbital 3) if there are equal energy
orbitals, electrons occupy them singularly before
pairing
Hund's Rule: there is a special stability associated with a half-filled or filled set of orbitals
Ionisation energy
When 1 mole of a gaseous element turns
into a mole of gaseous ions, freeing 1
mole of electrons
First ionisation energy: X(g) --> X^+ (g) + e^-
Second ionisation energy: X^+(g) --> x^2+(g) + e^-
Third ionisation energy: X^2+(g) --> x^3+(g) + e^-
Ionisation energy increases
successively (one follows the other)
because we are removing electrons
from an increasingly positive ion.
For Na, the 2nd I.E means taking energy from
a full inner shell- more nuclear attraction as it
is closer to the nucleus