English

Define the Bond enthalpy. - Chemistry

Advertisements
Advertisements

Question

Define the Bond enthalpy.

Definition

Solution

The enthalpy change required to break a particular covalent bond in one mole of the gaseous molecule to produce gaseous atoms and/or radicals is called bond enthalpy.

shaalaa.com
Thermochemistry
  Is there an error in this question or solution?
Chapter 4: Chemical Thermodynamics - Long answer questions

APPEARS IN

SCERT Maharashtra Chemistry [English] 12 Standard HSC
Chapter 4 Chemical Thermodynamics
Long answer questions | Q 2.1

RELATED QUESTIONS

Answer in brief.

How much heat is evolved when 12 g of CO reacts with NO2? The reaction is:

4CO(g)  2NO2(g) → 4CO2(g) + N2(g), ΔrH° = - 1200 kJ


Answer the following question.

Calculate ΔrH° for the following reaction at 298 K:

1) 2H3BO3(aq) → B2O3(s) + 3H2O(l), ΔrH° = + 14.4 kJ

2) H3BO3(aq) → HBO2(aq) + H2O(l), ΔrH° = - 0.02 kJ

3) H2B4O7(s) → 2B2O3(s) + H2O(l), ΔrH° = + 17.3 kJ


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]


Calculate enthalpy of formation of HCl if bond enthalpies of H2, Cl2 and HCl are 434 kJ mol-1, 242 kJ mol–1 and 431 kJ mol–1 respectively.


Define the Standard enthalpy of combustion.


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


The enthalpy change of the following reaction:

\[\ce{CH_{4(g)} + Cl_{2(g)} -> CH3Cl_{(g)} + HCl_{(g)}ΔH^0 = –104 kJ}\]

Calculate C – Cl bond enthalpy. The bond enthalpies are:

Bond C − H Cl − Cl H − Cl
∆H°/kJ mol−1 414 243 431

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 

Define the Enthalpy of ionisation.


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


Classify the following into intensive and extensive properties.

Pressure, volume, mass, temperature.


A compound that has a high negative heat of formation is normally ____________.


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


The heat of formations of CO(g) and CO2(g) are −26.4 kcal and −94.0 kcal respectively. The heat of combustion of carbon monoxide will be ____________.


lf, \[\ce{C_{(s)} + O2_{(g)} -> CO2_{(g)}}\], ∆H = x .........(i)

\[\ce{CO_{(g)} + 1/2O2_{(g)} -> CO2_{(g)}}\], ∆H = y .......(ii)

Then, the heat of formation of CO is:


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?


Calculate the enthalpy of hydrogenation of C2H4(g), given that the enthalpy of formation of ethane and ethylene are −30.2 kcal and +12.5 kcal respectively.


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?


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. \[\ce{H2_{(g)} + 1/2 O2_{(g)} -> H2O_{(l)}Δ_fH^° = - 286 kJ mol^{-1}}\]

\[\ce{A -> B}\], ∆H = −10 kJ mol−1, Ea(f) = 50 kJ mol−1, then Ea of \[\ce{B -> A}\] will be ______.


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


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)


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

ΔcH0[CH3CHO(l)] = - 1166 kJ mol-1


The heat evolved in the combustion of 6.022 x 1021 carbon particles is 3.94 kJ. The heat of combustion of carbon is ______.


For the reaction, H2 + I2 ⇌ 2HI; ΔH = 12.4 kcal. The heat of formation of HI, ΔHf = ______.


Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×