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प्रश्न
Select the most appropriate option.
The enthalpy of formation for all elements in their standard states is _______.
पर्याय
unity
zero
less than zero
different elements
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उत्तर
The enthalpy of formation for all elements in their standard states is zero.
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संबंधित प्रश्न
Select the most appropriate option.
If the standard enthalpy of formation of methanol is –238.9 kJ mol–1 then entropy change of the surroundings will be _______.
Obtain the relationship between ΔH and ΔU for gas phase reactions.
Calculate the work done in the decomposition of 132 g of \[\ce{NH4NO3}\] at 100°C.
\[\ce{NH4NO3_{(s)} -> N2O_{(g)} + 2H2O_{(g)}}\]
State whether work is done on or by the system.
Answer the following question.
Calculate standard enthalpy of reaction,
Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g), from the following data.
Δf H°(Fe2O3) = - 824 kJ/mol,
Δf H°(CO) = - 110 kJ/mol,
Δf H°(CO2) = - 393 kJ/mol
Calculate the standard enthalpy of formation of \[\ce{CH3OH_{(l)}}\] from the following data:
\[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)} }\]; ΔrH° = − 726 kJ mol-1
\[\ce{C_{(graphite)} + O2_{(g)} -> CO2_{(g)}}\]; ΔcH° = −393 kJ mol−1
\[\ce{H2_{(g)} + 1/2 O_{(g)} -> H2O_{(l)}}\]; ΔfH° = −286 kJ mol−1
Calculate the work done and comment on whether work is done on or by the system for the decomposition of 2 moles of NH4NO3 at 100 °C
NH4NO3(s) → N2O(g) + 2H2O(g)
Write the mathematical relation between ΔH and ΔU during the formation of one mole of CO2 under standard conditions.
Write the expression showing the relation between enthalpy change and internal energy change for gaseous phase reaction.
Define enthalpy of combustion.
Define enthalpy of neutralization.
Calculate the enthalpy change for the reaction \[\ce{Fe2O3 + 3CO -> 2Fe + 3CO2}\] from the following data.
\[\ce{2Fe + 3/2O2 -> Fe2O3}\]; ΔH = −741 kJ
\[\ce{C + 1/2O2 -> CO}\]; ΔH = −137 kJ
\[\ce{C + O2-> CO2}\]; ΔH = −394.5 kJ
The standard enthalpies of formation of SO2 and SO3 are −297 kJ mol−1 and −396 kJ mol−1 respectively. Calculate the standard enthalpy of reaction for the reaction: \[\ce{SO2 + 1/2O2 -> SO3}\]
The standard enthalpy of formation of ammonia is −46.0 kJ mol−1. The enthalpy change for the reaction:
\[\ce{2NH3_{(g)} -> 2N2_{(g)} + 3H2_{(g)}}\] is ____________.
Identify the equation in which change in enthalpy is equal to change in internal energy.
When 4 g of iron is burnt to ferric oxide at constant pressure, 29.28 kJ of heat is evolved. What is the enthalpy of formation of ferric oxide?
(Atomic mass of Fe = 56)
The enthalpy change for two reactions are given by the equations
\[\ce{2Cr_{(s)} + 1.5 O2_{(g)} -> Cr2O3_{(s)}}\];
∆H1 = −1130 kJ ............(i)
\[\ce{C_{(s)} + 0.5 O2_{(g)} -> CO_{(g)}}\];
∆H2 = −110 kJ .........(ii)
What is the enthalpy change, in kJ, for the following reaction?
\[\ce{3C_{(s)} + Cr2O3_{(s)} -> 2Cr_{(s)} + 3CO_{(g)}}\]
Given the bond energies N ≡ N, H – H and N – H bonds are 945, 436 and 391 kJ/mol respectively. The enthalpy of the reaction;
\[\ce{N2_{(g)} + 3H2_{(g)} -> 2NH3_{(g)}}\]
In which of the following reactions, ∆H is greater than ∆U?
Work done when 2 moles of an ideal gas is compressed from a volume of 5 m3 to 1 dm3 at 300 K, under a pressure of 100 kPa is ____________.
What is the amount of work done when 0.5 mole of methane, CH4 (g), is subjected to combustion at 300 K? (Given, R = 8.314 JK-1mol-1)
The work done during combustion of 9 × 10-2 kg of ethane, C2H6 (g) at 300 K is ______.
(Given R = 8.314 J deg-1, atomic mass C = 12, H = 1)
Calculate ΔU if 2 kJ heat is released and 10 kJ of work is done on the system.
Under what conditions ΔH = ΔU?
Calculate ΔS of the surrounding if the standard enthalpy of formation of methanol is − 238.9 kJ mol−1.
In a particular reaction, 2 kJ of heat is released by the system and 8 kJ of work is done on the system. Determine ΔU.
