Chemistry in Society Flashcards
bond enthalpies
the quantity of energy needed to break one mole of a bond in a gaseous molecule
measured in diatomic molecules (in data book)
chromatography
a qualitative technique used to separate out the components of mixtures to help identify the chemicals present in a mixture
dynamic equilibrium
acheived when the rates of the forward and reverse reactions are equal
the concentrations of reactants and products are constant (rarely equal)
endothermic
reaction
reaction which absorbs heat from the surroundings
+ΔH
enthalpy of combustion
the enthalpy change that occurs when one mole of a substance is burned completely in oxygen
enthalpy of neutralisation
the energy change when acid is neutralised to form one mole of water
enthalpy of solution
the energy change when one mole of a substance disolves in water
exothermic
reaction
reactions which release heat into the surroundings
-ΔH
feedstocks
- a reactant from which other chemicals can be extracted or synthesised
- they are derived from raw materials either by physical separation or by a chemical reaction
hess’s law
the enthalpy change for a chemical reaction is independant of the route taken, so long as the start and end point are the same for both routes
mean bond enthalpies
the quantity of energy needed to break bonds between gaseus atoms, averaged over different molecules that the bond can be found in
molar volume
volume occupied by one mole of atoms in the gaseous state is the same for all gases (at a constant pressure and temperature)
l mol-1
oxidising agent
a substance which accepts electrons and is reduced in the process
reducing agent
a substance which donates electrons and is oxidised in the process
retention time
in gas chromatography, it is the time taken for an individual peak to pass through the column after the injection time
specific heat capacity
formulae
Eh = cmΔT
can be used to find the enthalpy change of a reaction along with
ΔH = Eh/n
standard solution
definition
a solution of accurately known concentration
theoretical yield
the maximum possible amount of product in a reaction (if all the reactants have been converted into the product)
titration
determines the volume of reactant solution required to react completely with the test solution
volumetric analysis
using a standard solution in a quantitative reaction to determine the concentration of another substance
factors influencing industrial process design
- availability, sustainability and cost of feedstock(s)
- opportunities for recycling
- energy requirements
- marketability of by-products
- product yield
environmental considerations when designing industrial process
- minimising waste
- avoiding the use or production of toxic substances
- designing products which will biodegrade if appropriate
standard solution
process
- calculate mass needed through molar calculations
- weigh out solid using weigh boat and mass balance
- transfer solid into a beaker (wash weigh boat 3 times)
- add deionised water and stir until solid is completely dissolved
- transfer into volumetric flask and wash beaker and glass rod 3 times
- fill flask so bottom of meniscus on line
- stopper flask and invert
three types of chromatography
- paper chromatography
- thin layer chromatography
- gas chromatography
