The heat of combustion of solid benzoic acid at constant volume is -321.30kJ at 27oC . The heat of combustion at constant pressure is

Question

The heat of combustion of solid benzoic acid at constant volume is -321.30kJ at 27oC . The heat of combustion at constant pressure is (A)  -321.30-300R  (B)  -321.30+300R  (C)  -321.30-150R  (D)  -321.30-900R

Tardigrade Admin · Accepted Answer

C6H5COOH(s)+(15/2)O2(g) xrightarrow 7CO2(g)+3H2O(l) Δ ng=np-nr=7-(15/2)=(-1/2) qp=qv+Δ ng(RT) =-321.30+( -(1/2) )300R =-321.30-150R

Q. The heat of combustion of solid benzoic acid at constant volume is $- 321.30 k J$ at $27^{o} C$ . The heat of combustion at constant pressure is

$- 321.30 - 300 R$

$- 321.30 + 300 R$

$- 321.30 - 150 R$

$- 321.30 - 900 R$

$C_{6} H_{5} COO H (s) + \frac{15}{2} O_{2} (g)$ $7 C O_{2} (g) + 3 H_{2} O (l)$ $Δ n_{g} = n_{p} - n_{r} = 7 - \frac{15}{2} = \frac{- 1}{2}$ $q_{p} = q_{v} + Δ n_{g} (RT)$ $= - 321.30 + (- \frac{1}{2}) 300 R$ $= - 321.30 - 150 R$

Q. The heat of combustion of solid benzoic acid at constant volume is −321.30kJ at 27oC . The heat of combustion at constant pressure is

−321.30−300R

−321.30+300R

−321.30−150R

−321.30−900R