Advertisements
Advertisements
Question
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 |
Advertisements
Solution
Given: ΔrH0 = –104 kJ
ΔH0 (C – H) = 414 kJ mol–1
ΔH0 (Cl – Cl) = 243 kJ mol–1
ΔH0 (H – Cl) = 431 kJ mol–1
To find: C – Cl bond enthalpy, ΔH0 (C – Cl)
Formula: ΔrH0 = ∑ΔH°(reactant bonds) − ∑ΔH0 (product bonds)
Calculation: ΔrH0 = Σ ΔH0 (reactant bonds) – Σ ΔH0 (product bonds)
= [4 ΔH0(C – H) + ΔH°(Cl – Cl)] – [3 ΔH0(C – H) + ΔH0(C – Cl) + ΔH0(H – Cl)]
= ΔH0(C – H) + ΔH0(Cl – Cl) – ΔH0(C – Cl) – ΔH0(H – Cl) –104 kJ
∴ = 1 mol × (414 kJ mol–1) + 1 mol × (243 kJ mol–1) – ΔH0(C – Cl) – 1 mol × (431 kJ mol–1)
∴ –104 kJ = 226 kJ – ΔH°(C – Cl)
∴ ΔH0(C – Cl) = 226 kJ + 104 kJ
∴ ΔH0(C – Cl) = 330 kJ mol–1
C – Cl bond enthalpy is 330 kJ mol–1.
APPEARS IN
RELATED QUESTIONS
Select the most appropriate option.
Which of the following reactions is exothermic?
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.
Define the Standard enthalpy of combustion.
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.
Define the Enthalpy of ionisation.
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 ______.
The standard heats of formation for CCl4(g), H2O(g), CO2(g), and HCl(g) are −25.5, −57.8, −94.1 and −22.1 kcal mol−1, respectively.
∆H for the reaction
\[\ce{CCl4_{(g)} + 2H2O_{(g)} -> CO2_{(g)} + 4HCl_{(g)}}\] at 298 K
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 enthalpy change accompanying a reaction in which 1 mole of the substance in the standard state reacts completely with oxygen or is completely burnt is called as ____________.
\[\ce{S + 3/2O2 -> SO3 +2{x} kcal}\] .........(i)
\[\ce{SO2 + 1/2O2 -> SO3 + {y} kcal}\] .......(ii)
The heat of formation of SO2 is ____________.
Which among the following salts, solubility decreases with increase in temperature?
Which of the following compounds is Not present in its standard state at 25°C and 1 atmosphere pressure?
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)?
Calculate the standard enthalpy of formation of CH3OH(l) from the following data:
- \[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)}ΔH^° = - 726 kJ mol^{-1}}\]
- \[\ce{C_{(s)} + O2_{(g)} → CO2_{(g)}Δ_cH^° = – 393 kJ mol^{-1}}\]
- \[\ce{H2_{(g)} + 1/2 O2_{(g)} -> H2O_{(l)}Δ_fH^° = - 286 kJ mol^{-1}}\]
Calculate the standard enthalpy of:
\[\ce{N2H_{4(g)} + H_{2(g)} -> 2NH_{3(g)}}\]
If ΔH0(N – H) = 389 kJ mol–1, ΔH0(H – H) = 435 kJ mol–1, ΔH0(N – N) = 159 kJ mol–1.
From the following bond energies:
H – H bond energy: 431.37 kJ mol−1
C = C bond energy: 606.10 kJ mol−1
C – C bond energy: 336.49 kJ mol−1
C – H bond energy: 410.50 kJ mol−1
Enthalpy for the given reaction will be:
\[\begin{array}{cc}
\phantom{}\ce{H}\phantom{...}\ce{H}\phantom{...................}\ce{H}\phantom{...}\ce{H}\phantom{....}\\
\phantom{.}|\phantom{....}|\phantom{....................}|\phantom{....}|\phantom{.....}\\
\ce{C = C + H - H -> H - C - C - H}\\
\phantom{.}|\phantom{....}|\phantom{....................}|\phantom{....}|\phantom{.....}\\
\phantom{}\ce{H}\phantom{...}\ce{H}\phantom{...................}\ce{H}\phantom{...}\ce{H}\phantom{....}
\end{array}\]
How many moles of helium gas occupies 22.4 Lat 0°c and at 1 atmospheric pressure?
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 ______.
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)
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.
The enthalpy of combustion of S (rhombic) is − 297 kJ mo1-1. Calculate the amount of sulphur required to produce 29. 74 kJ of heat.
Calculate ΔsubH of the H2O from the given data:
\[\ce{H2O_{(s)}->H2O_{(l)},}\] ΔfusH = 6.01kJ mol−1
\[\ce{H2O_{(l)}-> H2O_{(g)},}\] ΔVapH = 45.07 kJ mol−1.
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.
