Delta S is positive for the reaction. CaO(s) + CO_2(g) rightarrow CaCO_1(s) N_2(

Question

Delta S is positive for the reaction. CaO(s) + CO_2(g) rightarrow CaCO_1(s) N_2(g) + 3H_2(g) rightarrow 2 NH_1(g) 2SO_1(g) rightarrow 2SO_2(g) + O_2(g) Ag (aq) + CI (g) rightarrow AgCI(s) H_2O(I) rightarrow H_2O(s) The mechanism of a reaction is shown below. What is the overall reaction? Overall reaction: Which compounds are intermediates? Intermediates: Predict the rate law based on this mechanism. Predicted mechanism: What is the overall order of the reaction? HOOH + I rightarrow HOI + OH (slow) HOI + I rightarrow I_2 + OH (fast) 2OH + 2H_1O^+ rightarrow 4 H_20 (fast) For the reaction A + B rightarrow C, the rate constant at 215 degree C is 5.0 times 10^-3 and the rate constant at 452 degree C is 1.2 times 10^-1. What is the activation energy in kJ/mol? What is the rate constant at 100 degree C.

Explanation / Answer

1)The entropy change for a reaction is positive if there are more moles of product gas than there are of reactant gas. in this case for the reaction, 2SO3------------> 2SO2(g) +O2(g) this happnes and entropy change is +ve. for the reaction Ag+(aq) +Cl-(aq)-------> AgCl(s) liquid becomes solid and degress of disorder ( which is an indication of entropy) decreases

2. In a chemical reaction involving non-elementary reaction the slowest step is the rate detemining step.

addition of reactions 1 and 2 gives HOOH +2I- ------> HOI +I2 +2OH-

Addition of this to third reaction gives HOOH+2I-+2H3O+------->I2+ 4H2O

So intermediatres are OH- and HOI-, rate law= K[ HOOH] [I-]

3.   From Arhenius equation ln (K2/K1)= (Ea/R)*(1/T1-1/T2), T1= 215 deg.c =215+273.15 =488.15K and T2= 452 deg.c =452+273.15= 725.15 K

ln (1.2*10-4/5*10-5) = (Ea/R)*(1/488.15-1/725.15)= (Ea/R)*0.00067

Ea/R = 1308

Ea= 1308*8.314=10875 joules

at 100 deg.c let T1= 100 deg.c =100+273.15 =373.15 T2= 725.15

ln(1.2*10-4)/K1)= 1308*(1/373.15-1/725.15)=1308*0.001301=1.7

1.2*10-4/K1= 5.5

K1= 1.2*10-4/5.5=2.18*10-5

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