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प्रश्न
Select the most appropriate option.
The enthalpy of formation for all elements in their standard states is _______.
विकल्प
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 _______.
Select the most appropriate option.
Bond enthalpies of H–H, Cl–Cl, and H–Cl bonds are 434 kJ mol–1, 242 kJ mol–1, and 431 kJ mol–1, respectively. Enthalpy of formation of HCl is _______.
Answer in brief.
Obtain the expression for work done in chemical reaction.
Calculate the amount of work done in the
1) Oxidation of 1 mole HCl(g) at 200 °C according to reaction.
4HCl(g) + O2(g) → 2Cl2(g) + 2H2O(g)
2) Decomposition of one mole of NO at 300 °C for the reaction
2NO(g) → N2(g) + O2(g)
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.
An ideal gas expands from the volume of 1 × 10–3 m3 to 1 × 10–2 m3 at 300 K against a constant pressure at 1 × 105 Nm–2. The work done is
Define enthalpy of combustion.
Define enthalpy of neutralization.
Enthalpy of neutralization is always a constant when a strong acid is neutralized by a strong base: account for the statement.
Derive the relation between ∆H and ∆U for an ideal gas. Explain each term involved in the equation.
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: \[\ce{SO2 + 1/2O2 -> SO3}\]
Identify the equation in which change in enthalpy is equal to change in internal energy.
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 ____________.
If 2 kJ of heat is released from system and 6 kJ of work is done on the system, what is enthalpy change of system?
In which of the following reactions, ΔH is not equal to ΔU?
Calculate the work done during the combustion of 0.138 kg of ethanol, C2H5OH(l) at 300 K.
Given: R = 8.314 Jk−1 mol−1, molar mass of ethanol = 46 g mol−1.
Under what conditions ΔH = ΔU?
Calculate ΔS of the surrounding if the standard enthalpy of formation of methanol is − 238.9 kJ mol−1.
Calculate work done in oxidation of 4 moles of SO2 at 25°C. (Given: R = 8.314 JK−1 mol−1 ).
