The combustion enthalpy of carbon, hydrogen and methane are -393.5;-284.8 and -890.4kJ/mole respectively at 25° C . The value of standard formation enthalpies of methane at that temperature is :-

Question

The combustion enthalpy of carbon, hydrogen and methane are -393.5;-284.8 and -890.4kJ/mole respectively at 25° C . The value of standard formation enthalpies of methane at that temperature is :- (A) 890.4kJ/mole (B) -298.8kJ/mole (C) -72.7kJ/mole (D) -107.7kJ/mole

Tardigrade Admin · Accepted Answer

C+2H2 arrow CH4 ΔHR=Δ CHC+2× Δ CHH2-Δ CHCH4

Q. The combustion enthalpy of carbon, hydrogen and methane are $- 393.5; - 284.8$ and $- 890.4 k J / m o l e$ respectively at $2 5^{\circ} C$ . The value of standard formation enthalpies of methane at that temperature is :-

$890.4 k J / m o l e$

$- 298.8 k J / m o l e$

$- 72.7 k J / m o l e$

$- 107.7 k J / m o l e$

$C + 2 H_{2} \to C H_{4}$
$Δ H_{R} = Δ_{C} H_{C} + 2 \times Δ_{C} H_{H_{2}} - Δ_{C} H_{C H_{4}}$

Q. The combustion enthalpy of carbon, hydrogen and methane are −393.5;−284.8 and −890.4kJ/mole respectively at 25∘C . The value of standard formation enthalpies of methane at that temperature is :-

890.4kJ/mole

−298.8kJ/mole

−72.7kJ/mole

−107.7kJ/mole