9. Balances on Molecular and Atomic species
Balances work on the principle that atoms can neither be created nor destroyed in a chemical reaction.
Example the reaction 2H₂ + O₂ 
2H₂O where x represents the unknown mol H₂ that is fed into the system and y mol H₂O is produced also z the 0₂ that is in the feed.
2H₂O where x represents the unknown mol H₂ that is fed into the system and y mol H₂O is produced also z the 0₂ that is in the feed.
We can perform a hydrogen balance on the reaction which could mean an atomic balance or a molecular balance.
Water molecular balance would be generation=output
Generated H₂0 (mol H₂0 generated/min) =y mol H₂0/min
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Hydrogen molecular balance would be input= output +consumption
x mol H₂/min = x(mol H₂ generated/min) + consumption H₂(mol H₂/min)
Oxygen molecular balance would be generation=output
Gen O₂ (mol O₂ generated/min) =z mol(O₂/min)
Atomic balance works on the same principle expect with the number of each atoms of elements in the molecule example Atomic hydrogen balance would be: input=output
xMol H₂(feed) x 2 mol H(Which represents the two hydrogen’s)= x mol H₂ (output)x 2 mol H(hydrogen’s in water) x 2( stoichiometry)
Extend of reaction can be used as followed:
Atomic species balances lead to direct solution technique when more than one reaction is involved
Extents of reactions are useful for chemical equilibrium problems and when equation solving software is to be used.
Molecular species require more complex calculations than the other methods and is recommended for simple systems with one reaction
Independents can be defined as one thing that is independent of another; they are detached and not associated, so the first one is not affected or subjective by the second.
Independent equations: Algebraic equations are independent if it is not possible to obtain them by adding and subtracting any other equations.
If two molecular species are in the same ratio anyplace they appear in a process to one and other and this ratio is incorporated in the flow chart labeling, balances on those species are not independent equations.
With other words chemical reactions are independent of the stoichiometry equation if any other equation cannot be obtained by adding and multiplying and etc. of any other stoichiometry equation.
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