Question

consider the table of average bond enthalpies.
what is the \\( \delta h \\) (in \\( kj \\)) for the combustion of methane?
round your answer to a whole number. if your answer is negative, include the sign.
\\( \mathrm { ch } _ { 4 } ( g ) + 2 \mathrm { o } _ { 2 } ( g ) \
ightarrow \mathrm { co } _ { 2 } ( g ) + 2 \mathrm { h } _ { 2 } \mathrm { o } ( g ) \\)

Explanation:

Step1: Calculate energy required to break bonds

• For \(CH_4\): There are \(4\) \(C - H\) bonds. Energy to break \(CH_4\) bonds: \(4\times413=1652\) kJ.
• For \(O_2\): There are \(2\) \(O = O\) bonds. Energy to break \(O_2\) bonds: \(2\times495 = 990\) kJ.
• Total energy to break bonds: \(1652+990=2642\) kJ.

Step2: Calculate energy released from forming bonds

• For \(CO_2\): There are \(2\) \(C = O\) bonds. Energy released from \(CO_2\) bonds: \(2\times799 = 1598\) kJ.
• For \(H_2O\): There are \(2\times2 = 4\) \(O - H\) bonds. Energy released from \(H_2O\) bonds: \(4\times463=1852\) kJ.
• Total energy released: \(1598 + 1852=3450\) kJ.

Step3: Calculate \(\Delta H\)

Using the formula \(\Delta H=\text{Energy to break bonds}-\text{Energy released from forming bonds}\)
\(\Delta H=2642-3450=-808\) kJ.

Answer:

\(-808\)