The variation of equilibrium constant ( K) with temperature ( T) was stupied by plotting log K versus 1/T The plot obtained is shown iin the Fig . Hence, enthalpy change `(Delta H^(@))` of the reaction is

Options

A. ` + 2 cal`
B. `-2 cal`
C. `+ 4.606 cal`
D. ` - 4.606 cal`

Answer

D

Explanation

According to van't Hoff equation ,
` log K= (Delta H^(@))/(2.303 RT) + "constant "`
` :. Plot of log K vs 1//T is linear with slope `
` = (Delta H^(@))/(2.303 R)`
Slope = `tan theta = tan 45^(@) = 1` . Hence , `Delta H^(@) = - 2.303 R`
` = - 2.303 xx 2 cal = - 4.606 cal `