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प्रश्न
Assertion (A): Combustion of all organic compounds is an exothermic reaction.
Reason (R): The enthalpies of all elements in their standard state are zero.
पर्याय
Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.
उत्तर
Both A and R are true but R is not the correct explanation of A.
Explanation:
The enthalpy of the reactants is always greater than the enthalpy of the product in a combustion reaction.
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संबंधित प्रश्न
ΔU⊖of combustion of methane is – X kJ mol–1. The value of ΔH⊖ is ______.
The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are, - 890.3 kJ mol-1 -393.5 kJ mol-1, and - 285.8 kJ mol-1 respectively. Enthalpy of formation of CH4(g) will be ______.
Standard enthalpy of combustion at 25°C of hydrogen, cyclohexene (C6H10) and cyclohexane (C6H12) are – 240, – 3800 and – 3920 kJ/mol respectively. The heat of hydrogenation of cyclohexene is ______.
At 25°C and 1 atm pressure, the enthalpies of combustion are as given below:
| Substance | H2 | C (graphite) | C2H6(g) |
| `(Δ_"c""H"°)/"kJ mol"^-1` | −286 | −394 | −1560 |
The enthalpy of the formation of ethane is:
