When Do Reactions Achieve Equilibrium

1
When Do Reactions Achieve Equilibrium?

• Need to look at 2 factors
• ENTHALPY
• (heat content)
• and
• ENTROPY
• (degree of randomness)
• Chemical reactions strive towards
• MINIMUM ENTHALPY and MAXIMUM ENTROPY
• want to be cool want to be messy
• favours exo rxns favours gases
• always point favouring ( g gt aq gt l gt s)
• arrow toward heat term
• Ex. A(s) B(l) ? C(l) D(g) energy
• ? minimum enthalpy
• ? maximum entropy
• Since both factors favour the forward direction
  (toward products), reaction is said to go to
  completion

2

• Be careful of the wording of the question!
• Ex. 4A(g) ? B(g) 2C(s) heat
• What applies to the forward reaction?
• ? minimum enthalpy
• ? maximum entropy ? minimum entropy
• The enthalpy is decreasing in the forward
  reaction, as is the entropy
• Do entropy/enthalpy 1