Confusion about Stoichiometric coefficients

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SUMMARY

The discussion clarifies the distinction between stoichiometric coefficients (v's) and actual amounts of components (n's) in a chemical reaction equilibrium context. Stoichiometric coefficients, represented as v_A, v_B, v_C, and v_D, indicate the theoretical proportions of reactants and products involved in the reaction, while n_A, n_B, n_C, and n_D denote the actual moles present in the system. The relationship between these variables is expressed through the equation -dn_A/v_A = -dn_B/v_B = dn_C/v_C = dn_D/v_D, highlighting how changes in the amounts of components relate to their stoichiometric coefficients. This understanding is essential for analyzing reaction dynamics in thermodynamics.

PREREQUISITES
  • Understanding of chemical reaction equilibrium
  • Familiarity with stoichiometric coefficients
  • Basic knowledge of thermodynamics principles
  • Ability to interpret mathematical relationships in chemical equations
NEXT STEPS
  • Study the concept of chemical reaction kinetics
  • Learn about the application of the ideal gas law in reaction equilibrium
  • Explore the relationship between extensive and intensive properties in thermodynamics
  • Investigate the use of reaction quotient (Q) in determining reaction direction
USEFUL FOR

Chemical engineers, thermodynamics students, and anyone studying chemical reaction dynamics will benefit from this discussion, particularly those seeking to understand the role of stoichiometric coefficients in reaction equilibrium analysis.

Saladsamurai
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Hey folks! I am studying from a thermodynamics text (engineering thermo) and I am a little confused with the wording in the following development of the "Equation of Reaction Equilibrium":

Text said:
Consider a closed system containing 5 components A, B , C, D and E. We will assume tha E is inert and thus does not appear in the rxn:

v_AA +v_BB \leftrightharpoons v_CC + v_DD \qquad(1)​

where the v's are the stoichiometric coefficients. Note that the stoichiometric coefficients v_A, v_B, v_C, v_D do not correspond to the respective number of moles present. The amounts of components are designated n_A,n_B,n_C,n_D. However the, changes in the amounts of components present do bear a relationship to the values of the stoichiometric coefficients. That is,

<br /> -\frac{dn_A}{v_A}=-\frac{dn_B}{v_B}=\frac{dn_C}{v_C}=\frac{dn_D}{v_D}\qquad(2)<br />​

I am a little confused as to the distinction between the n's and the v's. Is it saying that the n's are the actual amounts present whereas the v's are the theoretical amounts needed for a balanced reaction?Thanks!
~Casey
 
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Saladsamurai said:
Hey folks! I am studying from a thermodynamics text (engineering thermo) and I am a little confused with the wording in the following development of the "Equation of Reaction Equilibrium":



I am a little confused as to the distinction between the n's and the v's. Is it saying that the n's are the actual amounts present whereas the v's are the theoretical amounts needed for a balanced reaction?


Thanks!
~Casey

Stochiometric coefficients describe the relative rates of reaction for the different reactants and products, you could say.

Another way to look at it is that for every va moles of A participate in the reaction, vb moles of B will also participate, vc moles of C and vd moles of D will be produced.

Hope that clears things up.
 
I think you understand the text perfectly.
It is very like an extensive property vs and intensive property in this description.