Answer:
+ 291.9 kJ
Solution:
The equation given is as;
H₂O ₍s₎ → H₂ ₍g₎ + 1/2 O₂ ₍g₎ ΔH = ?
First, as we know the heat of formation of H₂O ₍l₎ is,
H₂ ₍g₎ + 1/2 O₂ ₍g₎ → H₂O ₍l₎ ΔH = - 285.9 kJ
Now, reversing the equation will reverse the sign of heat as,
H₂O ₍l₎ → H₂ ₍g₎ + 1/2 O₂ ₍g₎ ΔH = + 285.9 kJ
Also, we know that,
H₂O ₍s₎ → H₂O ₍l) ΔH = + 6.0 kJ
Now, adding last two equations,
H₂O ₍l₎ → H₂ ₍g₎ + 1/2 O₂ ₍g₎ ΔH = + 285.9 kJ
H₂O ₍s₎ → H₂O ₍l) ΔH = + 6.0 kJ
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H₂O ₍s₎ → H₂ ₍g₎ + 1/2 O₂ ₍g₎ ΔH = + 291.9 kJ
