Ivory asked:
energy released in the formation of 1 mol H2 from hydrogen atoms? The bond energy of H2 is 435 kJ/mol
The answer is 1400g
But i dont know how they got that. What formula or conversion factor are we sopposed to use. Im so confused. Please help 
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Enthalpie = (CP x T x m) / (1000 x n) Wanneer enthalpie is 435, CP is 4,18 (energie-dichtheid van water), T is de verandering in temperatuur (100 – 25), m is de massa van water (haar wat je wilt), n is de mol van waterstof gas (1) . Daarom opnieuw geordend geeft: m = (enthalpie x 1000 x n) / (CP x T) Het antwoord is 1387g = 1400g (2 s.f.)