a) Qualitatively predict whether the reaction will be product or reactant favore
ID: 968303 • Letter: A
Question
a) Qualitatively predict whether the reaction will be product or reactant favored.
b) Use your data to verify your prediction. Calculate the value of equilibrium constant for this reaction at 25 oC.
c) Discuss the effect of increasing temperature on the extent of the reaction.
LET'S THINK Thermodynamic Analysis The reaction between methyl chloride (CH,CI) and hydroxide ions (OH) in water to produce methanol (CH,OH) represented in Figure 7.7 is a typical example of a sub- stitution reaction. Relevant thermodynamicOH(aq) So (kJ/mol) (J/(mol K) CH,CI(g)225.61.05 x 101-83.68 234..4 -10.5 CH,OH( 355.8 miscible-238.4127.2 55.1 evant thermodynamic OH 229.9 data are listed in the table: Qualitatively predict whether the reac C(aq) tion will be product or reactant favored. 167.4 Use your data to verify your prediction. Calculate the value of the equilibrium constant for this reac- tion at 25 C Discuss the effect of increasing temperature on the extent of the reaction.Explanation / Answer
CH3Cl + OH- -------> CH3OH+ Cl-
Enthalpy of reaction = Enthalpy of products- Enthalpy of reactants=
=-238.4-167.4+(229.9+83.68) =-92.22 Kj.mol. The reaction is exothermic
Entropy change= 127.2+55.1- (234.4-10.5)= -41.6 J/mole.K=-0.0416 Kj/mole.K
gibbs free energy change = Enthalpy change-T* entropy change= -92.2+298.15*0.0416=-79.797 Kj/mole
since Gibbs free energy is -ve, the reaction is spontaneous and product favored.
Gibbs free energy change= -RTlnK
=79.797*1000= 8.314*298.15lnK
lnK= 79.797*1000/(8.314*298.15)=32.19
K= 9.56*1013 = [CH3OH] [Cl-]/ [CH3Cl-] [OH-]
Large K value suggest more of product and less of reactants.
Since the reaction is exothermic, as temperature is increased, the reaction proceeds in a direction of decreasing temperature, i.e endothermic direction. So reactant favored.
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