Summary mass balances

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Summary mass balances
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Quantifying matter

• Two ways
• mass
• mols
• Different units possible
• g, kg, lb, etc.
• mol, kg-mol, lb-mol,etc

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Quantifying mixtures

• Many ways
• Mass fractions, percents
• Mol fractions, percents
• Ratio of mols
• Ratio of masses

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Conservation of mass

• Balancing the chemical reaction
• Equalizing the number of atoms of each element in
  the reactants (left side of equation) and
  products (right side of the equation)
• We can also do this with the total mass of each
  type of atom instead of the number.
• Both express the same principle.
• It is easier to do it with the number of atoms

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Conservation of mass

• Balancing the chemical reaction does not cover
  all situations
• Excess reactant
• Inerts
• Incomplete reaction

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Systems

• Flow (open) systems defined by the streams that
  enter and leave
• Streams contain one or more components
• Each component may be made up of one or more
  elements

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System Material Balances

• The number (mass) of atoms of each element in the
  feed streams must be equal to the number (mass)
  in the product streams.
• We can also keep track of molecular components
  but if they react we cannot write inputoutput
• We write this equation using the available
  information about the streams and by using
  algebraic symbols for the unknown quantities.
• We solve for the unknowns using the equations

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System Material Balances

• Equations that can be written
• Elemental balances
• Compound balances
• total mass balance
• Not all of them are independent

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Summary Gases, Vapours

• PV NRT
• P pa pb pc .
• V total va vb vc .
• pf(T)