English

Define the Standard enthalpy of combustion - Chemistry

Advertisements
Advertisements

Question

Define the Standard enthalpy of combustion.

Definition

Solution

The standard enthalpy of combustion of a substance is the standard enthalpy change accompanying a reaction in which one mole of the substance in its standard state is completely oxidized.

shaalaa.com
Thermochemistry
  Is there an error in this question or solution?
Chapter 4: Chemical Thermodynamics - Short answer questions (Type- I)

RELATED QUESTIONS

Answer the following in one or two sentences.

What is standard state of a substance?


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.


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.


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 

Define the Bond enthalpy.


Write an application of Hess’s law.


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


When 6.0 g of graphite reacts with dihydrogen to give methane gas, 37.4 kJ of heat is liberated. What is standard enthalpy of formation of CH4 (g)?


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 ____________.

\[\ce{2NO2_{(g)} ⇌ N2O4_{(g)}}\]


Which among the following salts, solubility decreases with increase in temperature?


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


Given the reaction,

\[\ce{CH2O_{(g)} + O2_{(g)} -> CO2_{(g)} + H2O_{(g)}}\] ΔH = −527 kJ

How much heat will be evolved in the formation of 60 g of CO2?


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 ______.


Standard entropies of N2(g), H2(g), and NH3(g) are a1, a2 and a3 J K-1 mol-1 respectively. What is value of ΔS° for formation of NH3(g)?


Which of the following equations has ΔfH° and ΔH° same?


Heat of formation of ethane, ethylene acetylene and carbon dioxide are - 136, - 66, - 228 and - 395 (all in kJ) respectively, most stable among them is ______.


Calculate the standard enthalpy of formation of CH3OH(l) from the following data:

  1. \[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)}ΔH^° = - 726 kJ mol^{-1}}\]
  2. \[\ce{C_{(s)} + O2_{(g)} → CO2_{(g)}Δ_cH^° = – 393 kJ mol^{-1}}\]
  3. \[\ce{H2_{(g)} + 1/2 O2_{(g)} -> H2O_{(l)}Δ_fH^° = - 286 kJ mol^{-1}}\]

Identify the invalid equation.


When the enthalpy of combustion of carbon to carbon dioxide is - 360 kJ mol-1, then the enthalpy change for the formation of 18 g of CO2 from carbon and dioxygen at the same temperature in kJ will be ______.


When 0.5 gram of sulphur is burnt to form SO2, 4.6 kJ of heat liberated. Calculate enthalpy of formation of SO2(g). (Atomic mass : S = 32, O = 16)


Calculate the standard enthalpy of the reaction:

SiO2(s) + 3C(graphite) → SiC(s) + 2CO(g) from the following reactions:

  1. Si(s) + O2(g) → SiO2(s), ΔrH° = −911kJ
  2. 2C(graphite) + O2(g) → 2CO(g), Δr = −221kJ
  3. Si(s) + C(graphite) → SiC(s), Δr = −65.3kJ

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.


Draw energy profile diagram and show:

  1. activated complex
  2. energy of activation for forward and backward reactions
  3. enthalpy of reaction

Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×