If the heat of formation of H2O(l) is –286 kJ/mol, which of the following thermochemical equations is correct?
(a) 2 H(g) + O(g) H2O(1)
AH = -286 kJ
(b) 2 H2(g) + O2(g) 2 H2O(1)
AH = -286 kJ
(c) H2(g) + 3 02(8) H2O(0
AH = -286 kJ
(d) H2(g) + O(g) →→ H2O(g)
AH = -286 kJ
(e) H2O(1) H2(g) + 2 02(8)
AH = -286 kJ
Practice Exercise 2

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

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answer: gold foil experiment - he shot alpha particles at a gold foil

explanation: