Discussion Forum

For the complete combustion of ethanol.   $C_{2}H_{5}OH(l)+3O_{2}(g)\rightarrow3CO_{2}(g)+3H_{2}O(l)$, the amount of heat  produced  as measured in bomb calorimeter, is 1364.47 kJ mol^-1  at 25° C. Assuring ideality the enthalpy of combustion, $\triangle_{C}H$, for the reaction  will be (R=8.314 JK^-1mol^-1)

Answer:

Explanation:

$C_{2}H_{5}OH(l)+3O_{2}(g)\rightarrow3CO_{2}(g)+3H_{2}O(l)$ 

$\triangle_{}U=-1364.47 kJ/mol$

$\triangle_{}H=\triangle_{}U+\triangle n_{g }RT$

 $\triangle n_{g }$  = -1

  $\triangle H=-1364.47+\frac{-1\times8.314\times298}{1000}$

 [Here, value of R in unit of J must be converted into kJ]

 =-1364.47-2.4776

 =-1366.94 kJ/mol

 During solving such problem, students are advised to keep much importance in unit conversion. As here, value of R 

(8.314 Jk^-1 mol^-1) in Jk^-1 mol^-1 must be converted into kJ by dividing the unit by 1000.