(a) Calculate the standard enthalpy of formation of

Chapter 3, Problem 104AE

(choose chapter or problem)

(a) Calculate the standard enthalpy of formation of gaseous diborane \(\left(\mathrm{B}_{2} \mathrm{H}_{6}\right)\) using the following thermochemical information:

\(4\mathrm{\ B}(s)+3\mathrm{\ O}_2(g)\longrightarrow2\mathrm{\ B}_2\mathrm{O}_3(s)\quad\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \Delta H^{\circ}=-2509.1\mathrm{\ kJ}\)

\(2\ \mathrm{H}_2(g)+\mathrm{O}_2(g)\longrightarrow2\mathrm{\ H}_2\mathrm{O}(l)\quad\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \Delta H^{\circ}=-571.7\mathrm{\ kJ}\)

\(\mathrm{B}_2\mathrm{H}_6(g)+3\mathrm{\ O}_2(g)\longrightarrow\mathrm{B}_2\mathrm{O}_3(s)+3\mathrm{\ H}_2\mathrm{O}(l)\quad\ \ \ \ \ \ \ \ \ \ \Delta H^{\circ}=-2147.5\mathrm{\ kJ}\)

(b) Pentaborane \(\left(\mathrm{B}_{5} \mathrm{H}_{9}\right)\) is another boron hydride. What experiment or experiments would you need to perform to yield the data necessary to calculate the heat of formation of \(\mathrm{B}_{5} \mathrm{H}_{9}(l)\)? Explain by writing out and summing any applicable chemical reactions.

Equation Transcription:

Text Transcription:

(B_2 H_6)

4 B(s) + 3 O_2 (g) rightarrow B_2 O_3 (s)

Delta H degree = -2509.1 kJ

2 H_2 (g) + O_2 (g) rightarrow 2 H_2 O(l)

Delta H degree = -571.7 kJ

B_2 H_6 (g) + 3 O_2 (g) rightarrow B_2 O_3 (s) + 3 H_2 O(l)

Delta H degree = -2147.5 kJ

(B_5 H_9)

B_5 H_9 (l)