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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता १२ वी

Does the following reaction represent a thermochemical equation? CHX4(g)+2OX2(g)⟶COX2(g)+2HX2OX(g), ∆fH° = –900 kJ mol–1

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प्रश्न

Does the following reaction represent a thermochemical equation?

\[\ce{CH_{4(g)} + 2O_{2(g)} -> CO_{2(g)} + 2H2O_{(g)}}\], ∆fH° = –900 kJ mol–1

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उत्तर

No, the given reaction does not represent a thermochemical equation. The given standard enthalpy of reaction (∆rH°) indicates the enthalpy change accompanying the reaction when the reactants and products involved are in their standard states. The standard state of water is H2O(l) and not H2O(g).

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पाठ 4: Chemical Thermodynamics - Long answer questions

संबंधित प्रश्‍न

Answer in brief.

How will you calculate reaction enthalpy from data on bond enthalpies?


Answer in brief.

What is the standard enthalpy of combustion? Give an example.


Answer the following question.

State Hess’s law of constant heat summation. Illustrate with an example. State its applications.


Calculate the total heat required

a) to melt 180 g of ice at 0 °C

b) heat it to 100 °C and then

c) vapourise it at that temperature.

[Given: ΔfusH° (ice) = 6.01 kJ mol-1 at 0 °C, ΔvapH° (H2O) = 40.7 kJ mol-1 at 100 °C, Specific heat of water is 4.18 J g-1 K-1]


The enthalpy change for the reaction, \[\ce{C2H4_{(g)} + H2_{(g)} -> C2H6_{(g)}}\] is −620 J when 100 mL of ethylene and 100 ml of \[\ce{H2}\] react at 1 bar pressure. Calculate the pressure volume type of work and ΔU for the reaction.


The standard enthalpy of formation of water is - 286 kJ mol-1. Calculate the enthalpy change for the formation of 0.018 kg of water.


State and explain Hess’s law of constant heat summation.


Calculate the standard enthalpy of combustion of CH4(g) if ΔfH°(CH4) = – 74.8 kJ mol–1, ΔfH°(CO2) = – 393.5 kJ mol–1 and ΔfH°(H2O) = – 285.8 kJ mol–1.


Calculate the standard enthalpy of formation of liquid methanol from the following data:

  1. \[\ce{CH3OH_{(l)} + \frac{3}{2} O_{2(g)} -> CO_{2(g)} + 2H2O_{(l)}}\]     ∆H° = – 726 kJ mol–1
  2. \[\ce{C_{(Graphite)} + O_{2(g)} -> CO_{2(g)}}\]          ∆cH° = – 393 kJ mol–1
  3. \[\ce{H_{2(g)} + \frac{1}{2} O_{2(g)} -> H2O_{(l)}}\]          ∆fH° = – 286 kJ mol–1 

Calculate the standard enthalpy of the reaction.

\[\ce{2Fe_{(s)} + \frac{3}{2} O_{2(g)} -> Fe2O_{3(s)}}\]

Given:

1. \[\ce{2Al_{(s)} + Fe2O_{3(s)} -> 2Fe_{(s)} + Al_2O_{3(s)}}\], rH° = –847.6 kJ
2. \[\ce{2Al_{(s)} + \frac{3}{2} O_{2(g)} -> Al2O_{3(s)}}\], rH° = –1670 kJ

Define the Enthalpy of ionisation.


Write an application of Hess’s law.


Classify the following into intensive and extensive properties.

Pressure, volume, mass, temperature.


The volume of oxygen required for complete combustion of 0.25 mole of methane at STP is ______.


Daily requirement of energy of a person is 'x' kJ. If heat of combustion of food material (Molecular mass = 100 g) is 'y' kJ, his daily consumption of the food in gram would be ____________.


The standard heats of formation in kcal mol−1 of NO2(g) and N2O4(g) are 8.0 and 2.0 respectively. The heat of dimerization of NO2 in kcal is ____________.

\[\ce{2NO2_{(g)} ⇌ N2O4_{(g)}}\]


Enthalpy of formation of two compounds x and y are −84 kJ and −156 kJ respectively. Which of the following statements is CORRECT?


Standard enthalpy of formation of water is - 286 kJ mol-1. When 1800 mg of water is formed from its constituent elements in their standard states the amount of energy liberated is ______.


Heat of formation of water is - 272 kJ mol-1. What quantity of water is converted to H2 and O2 by 750 kJ of heat?


Identify the invalid equation.


What is the amount of water formed by the combustion of 1.6 g methane?


The enthalpy change that accompanies a reaction in which 1 mole of its standard state is formed from its elements in their standard states


Standard enthalpy of combustion of a substance is given. Then Write thermochemical equation.

ΔcH0[CH3CHO(l)] = - 1166 kJ mol-1


Heat of combustion of methane is - 890 kJ/mol. On combustion of 12 gm of methane in excess of oxygen, ______ heat is evolved.


For the reaction, aA + bB → cC + dD, write the expression for enthalpy change of reaction in terms of enthalpies of formation of reactants and products.


Calculate heat evolved for combustion of 13 gm of acetylene (C2H2).

Given: \[\ce{C2H2_{(g)} + 5/2O_{2(g)}-> 2CO_{2(g)} + H2O_{(l)} \Delta_{(c)}H^{0} = - 1300 kJ}\]


Calculate the standard enthalpy of combustion of methane if the standard enthalpy of formation of methane, carbon dioxide and water are −74.8, −393.5 and −285.8 kJmol−1 respectively.


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