The reaction C4H10 ---> C2H6 + C2H4 has activation energy (Ea) of 450 kJ/mol, and the Ea of the reverse reaction is 250 kJ/mol. Estimate ΔH, in kJ/mol, for the reaction as written above.

ΔH = 200 kJ/mol

Explanation:

Step 1: Data given

activation energy (Ea) is:  450 kJ/mol

activation energy (Ea) of the reverse reaction is 250 kJ/mol

Step 2: The balanced equations

C4H10 ---> C2H6 + C2H4  Ea = 450 kJ/mol

C2H6 + C2H4 ---> C4H10    Ea = 250 kJ/mol

Step 3: Calculate ΔH

Since the reverse reaction has a lower activation energy, this means we need less reaction for the reverse reaction to happen. We can say the reaction absorbs energy, so this is the endothermic reaction.

Ea ( of the forward reaction) = ΔH + Ea (of the reverse reaction)

ΔH = Ea ( of the forward reaction) - Ea (of the reverse reaction)

ΔH = 450 kJ/mol - 250 kJ/mol

ΔH = 200 kJ/mol

Since the reactionis endothermi, ΔH is positive

when the volume of gas is   changed from   717.73 ml   to 852 ml   the temperature will   change   from 315   c to 452   c

    calculation

this is calculated using the charles law formula

that is,   v1/t1 = v2/t2

          v1=?

        t1 = 315 c   into   kelvin = 315 +273 = 588 k

        v2 = 852   ml

        t2 = 425c + 273 =698 k

make v1   the subject of the formula ( by   multiplying both side by t1)

  v1=( v2 xt1) / t2

v1= (852 ml   x 588 k)/ 698 k= 717.73 ml