1. Tardigrade
  2. Question
  3. Chemistry
  4. For the complete combustion of ethanol, C2H5OH(l) + 3O2(g) arrow 2CO2(g) + 3H2O(l), the amount of heat produced as measured in bomb calorimeter, is 1364.47 kJ mol-1 at 25°C. Assuming ideality the enthalpy of combustion, Δ CH, for the reaction will be (R = 8.314 J K-1 mol-1)

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Q. For the complete combustion of ethanol,
$C_2H_5OH_{(l)} + 3O_{2(g)} \rightarrow 2CO_{2(g)} + 3H_2O_{(l)},$
the amount of heat produced as measured in bomb calorimeter, is $1364.47 \,kJ \,mol^{-1}$ at $25^{\circ}C$. Assuming ideality the enthalpy of combustion, $\Delta_ CH$, for the reaction will be $(R = 8.314\, J \,K^{-1}$ $mol^{-1})$

JEE MainJEE Main 2014Thermodynamics

Solution:

$C _{2} H _{5} OH (l)+3 O _{2}(g) \longrightarrow 2 CO _{2}(g)+3 H _{2} O (l)$
$\Delta U=-1364.47\, kJ / mol$
$\Delta H=\Delta U+\Delta n_{g} R T$
$\Delta n_{g}=-1$
$\Delta H=-1364.47+\frac{-1 \times 8.314 \times 298}{1000}$
[Here, value of $R$ in unit of $J$ must be converted into $kJ$
$=-1364.47-2.4776=-1366.9476 \,kJ / mol$
or $=-1366.95 \,kJ / mol$