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

Question

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

Tardigrade Admin · Accepted Answer

C 6 H 5 COOH (s)+(15/2) O 2(g) arrow 7 CO 2(g)+3 H 2 O (l) Δ ng=np-nr=7-(15/2)=(-1/2) qp=qv+Δ ng(R T) =-321.30+(-(1/2)) 300 R =-321.30-150 R

Q. The heat of combustion of solid benzoic acid at constant volume is $- 321.30 k J$ at $2 7^{\circ} C$ . The heat of combustion at constant pressure is

$- 321.30 - 300 R$

$- 321.30 + 300 R$

$- 321.30 - 150 R$

$- 321.30 + 900 R$

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

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

−321.30−300R

−321.30+300R

−321.30−150R

−321.30+900R