For the gas phase isomerization of cis-cyanostyrene, cis-C6H5CH=CHC --> Ntrans-C6H5CH=CHCN the rate constant has been determined at several temperatures. When ln k in s-1 is plotted against the reciprocal of the Kelvin temperature, the resulting linear plot has a slope of -2.32×104 K and a y-intercept of 26.7. The activation energy for the gas phase isomerization of cis-cyanostyrene is ____ kJ/mol.

Respuesta :

Answer:

The activation energy for the gas phase isomerization of cis-cyanostyrene is 193 kJ/mol.

Explanation:

The relation between the rate constant (k) and the absolute temperature (T) is given by the Arrhenius equation:

[tex]k = A.e^{-Ea/R.T}[/tex]

where,

A is a preexponential factor

Ea is the activation energy

R is the ideal gas constant

T is the absolute temperature

This expression can be re-written like:

[tex]ln k = ln A -\frac{Ea}{R}.\frac{1}{T}[/tex]

The plot of ln k against 1/T gives a linear plot where ln A is the intercept and -Ea/R is the slope.

Since we know the slope is -2.32 × 10⁴ K, we can find Ea:

[tex]\frac{-Ea}{R} = -2.32 \times 10^{4} K\\Ea = -2.32 \times 10^{4} K \times -R\\Ea = -2.32 \times 10^{4} K \times (-8.314 \times 10^{-3} \frac{kJ}{K.mol})\\Ea = 193kJ/mol[/tex]

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