For the chemical equilibrium,
`CaCO_(3)(s) hArr CaO(s)+CO_(2)(g)`
`Delta_(r)H^(ɵ)` can be determined from which one of the following plots?

Options

A.
B.
C.
D.

Answer

A

Explanation

For the reaction,
`CaCO_(3(s))hArrCaO_((s))+CO_(2(g))`
`K_p=P_(CO_2) and K_C =[CO_2]`
`( :. [CaCO_3] = 1 and [CaO] =1 ` for solids)
According to Arrhenius equation we have `K=Ae^(-DeltaH_(r)^(@)//RT`
Taking logarithm, we have`logK_p = log A - (DeltaH_r^@)/(RT(2.303))`
This is an equation of straight line. When log `K_p` is plotted against 1 / T. we get a straight line.

The intercept of this line = log A, slope `= –DeltaH^@r// 2.303 R` Knowing the value of slope from the plot and universal gas constant `R, DeltaHr^@` can be calculated. Equation of straight line : Y = m x + C . Here, `logK_p =-(DeltaH_r^@)/(2.303R)(1/T)+logA`
`Y " " m " "x " "C`