Question

The energy of combustion of propane $\left(C_3{H}_8\right)$ gas in terms of given data is:
Bond energy (kJ/mol)
$$\begin{array}{ccccc}{ϵ}_{C-H}& {ϵ}_{O=O}& {ϵ}_{C=O}& {ϵ}_{O-H}& {ϵ}_{C-C}\\ +x_1& +x_2& +x_3& +x_4& +x_5\end{array}$$
Resonance energy of $C{O}_2$ is $-zkJ/mol$ and $△H_{vaporization}\left[H_{2}O\right]isykJ/mol$

• A. $8x_1+2x_5+5x_2-6x_3-8x_4-4y-3z$
• B. $6x_1+x_5+5x_2-3x_3-4x_4-4y-3z$
• C. $8x_1+2x_5+5x_2-6x_3-8x_4-y-z$
• D. $8x_1+2x_5+5x_2-6x_3-8x_4+4y+3z$

Answer 1

The correct option is D $8x_1+2x_5+5x_2-6x_3-8x_4+4y+3z$

$C_3{H}_8\left(g\right)+5O_2\left(g\right)\to 3C{O}_2\left(g\right)+4H_{2}O\left(l\right)△CH=[8\times B.E.(C-H)+2\times B.E(C-C)+5\times B.E(O=O\left)\right]-[6\times B.E(C=O)+8\times B.E.(O-H)+3]\times |R.E|ofC{O}_2+4\times △vapH\left(H_{2}O\right)$
$△H_{C_3{H}_8}$ = $[8\times (+x_1)+2\times (+x_5)+5\times (+x_2\left)\right]-[6\times +(x_3)+8\times (+x_4)+3\times (-z\left)\right)]+4\times (y)$
$=8x_1+2x_5+5x_2-6x_3-8x_4+4y+3z$