SATHEE: Thermodynamics and Thermochemistry 2 Question 19

Thermodynamics and Thermochemistry 2 Question 19

19. Compute the heat of formation of liquid methyl alcohol in $kJ {mol}^{- 1}$ , using the following data. Heat of vaporisation of liquid methyl alcohol $= 38 kJ / mol$ . Heat of formation of gaseous atoms from the elements in their standard states :

$H = 218 kJ / mol, C = 715 kJ / mol, O = 249 kJ / mol$ .

Average bond energies:

$(1997, 5 M)$

$C - H = 415 kJ / mol, C - O = 356 kJ / mol$ ,

$O - H = 463 kJ / mol$

Show Answer

Solution:

Given : $\mathrm{CH}{3} \mathrm{OH}(g) \longrightarrow \mathrm{CH}{3} \mathrm{OH}(l) ; \quad \Delta H=-38 \mathrm{~kJ}$

$C (g) + 4 H (g) + O (g) ⟶ {CH}_{3} OH (g)$

$Δ H = - (3 \times 415 + 356 + 463)$

$∵ H = H_{1} + H_{2} = - 2064 kJ$

$C (g) ⟶ C (g)$ ;

$Δ H = 715 kJ$

$$ \begin{aligned} 2 \mathrm{H}{2}(g) \longrightarrow & 4 \mathrm{H}(g) ; \ & \Delta H=2 \times 2 \times 218=872 \mathrm{~kJ} \ \frac{1}{2} \mathrm{O}{2}(g) \longrightarrow & \mathrm{O}(g) ; \quad \Delta H=249 \mathrm{~kJ} \end{aligned} $$

Adding : $C$ (gr) $+2 \mathrm{H}{2}(\mathrm{~g})+\frac{1}{2} \mathrm{O}{2}(\mathrm{~g}) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(l)$

$\begin{aligned} Δ H & = - 266 kJ / mol & = \frac{1 \times 1.25}{0.082 \times 300} \times 20.8 \times (189.86 - 300) J & = - 116.4 J \end{aligned}$

Thermodynamics and Thermochemistry 2 Question 19

19. Compute the heat of formation of liquid methyl alcohol in $kJ {mol}^{- 1}$ , using the following data. Heat of vaporisation of liquid methyl alcohol $= 38 kJ / mol$ . Heat of formation of gaseous atoms from the elements in their standard states :

Solution:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

Thermodynamics and Thermochemistry 2 Question 19

19. Compute the heat of formation of liquid methyl alcohol in kJmol−1, using the following data. Heat of vaporisation of liquid methyl alcohol =38 kJ/mol. Heat of formation of gaseous atoms from the elements in their standard states :

Solution:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

Menu

19. Compute the heat of formation of liquid methyl alcohol in $kJ {mol}^{- 1}$ , using the following data. Heat of vaporisation of liquid methyl alcohol $= 38 kJ / mol$ . Heat of formation of gaseous atoms from the elements in their standard states :