\(a)C_2^{}H_4^{} + 3O_2^{}\xrightarrow{{{t^o}}}2CO_2^{} + 2H_2^{}O\)

\(\Delta H_{298}^o = E_b^{}(C_2^{}H_4^{}) + 3.E_b^{}(O_2^{}) - 2E_b^{}(CO_2^{}) - 2.E_b^{}(H_2^{}O)\)

\(\Delta H_{298}^o = E_b^{}(C = C) + 4.E_b^{}(C - H) + 3.E_b^{}(O = O) - 2.2.E_b^{}(C = O) - 2.2.E_b^{}(O - H)\)

\(\Delta H_{298}^o = 1.(611 + 4.414) + 3.489 - 2.2.736 - 2.2.464 =  - 1066kJ\)

Phản ứng có delta âm nên xảy ra thuận lợi

\(b)C_2^{}H_6^{} + \frac{7}{2}O_2^{}\xrightarrow{{{t^o}}}2CO_2^{} + 3H_2^{}O\)

\(\Delta H_{298}^o = E_b^{}(C_2^{}H_6^{}) + \frac{7}{2}.E_b^{}(O_2^{}) - 2E_b^{}(CO_2^{}) - 3.E_b^{}(H_2^{}O)\)

\(\Delta H_{298}^o = E_b^{}(C - C) + 6.E_b^{}(C - H) + \frac{7}{2}.E_b^{}(O = O) - 2.2.E_b^{}(C = O) - 3.2.E_b^{}(O - H)\)

\(\Delta H_{298}^o =  - 1154kJ\)

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\(c)H_2^{} + \frac{1}{2}O_2^{}\xrightarrow{{{t^o}}}H_2^{}O\)

\(\Delta H_{298}^o = E_b^{}(H_2^{}) + \frac{1}{2}.E_b^{}(O_2^{}) - E_b^{}(H_2^{}O)\)

\(\Delta H_{298}^o = E(H - H) + \frac{1}{2}E_b^{}(O = O) - 2.E_b^{}(O - H) =  - 243kJ\)

Phản ứng có delta âm nên xảy ra thuận lợi

\(d)F_2^{} + H_2^{}O \to 2HF + \frac{1}{2}O_2^{}\)

\(\Delta H_{298}^o = E_b^{}(F_2^{}) + E_b^{}(H_2^{}O) - 2E_b^{}(HF) - \frac{1}{2}.E_b^{}(O_2^{})\)

\(\Delta H_{298}^o = E_b^{}(F - F) + 2.E_b^{}(O - H) - 2E_b^{}(H - F) - \frac{1}{2}.E_b^{}(O = O) =  - 292kJ\)

Phản ứng có delta âm nên xảy ra thuận lợi