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# AS energetics mcq watch

1. Methanol can be synthesised from methane and steam by a process that occurs in two stages. Stage 1 CH4(g) + H2O(g)= 3H2(g) + CO(g) is ∆H = +206 kJ mol–1 Stage 2 CO(g) + 2H2(g)= CH3OH(g) ∆H = –91 kJ mol–1 The standard enthalpies of combustion of carbon monoxide and of hydrogen are –283 kJ mol–1 and –286 kJ mol–1 , respectively. Use these data and the enthalpy change for Stage 2 to calculate a value for the standard enthalpy of combustion of gaseous methanol... Can u also tell me which one is correct? 1. Delta H= EnergyIn (reactants)-EnergyOut(products) 2.DeltaH=Products-reactants ∆H = Σ∆Hc ο (reactants) – Σ∆Hc ο (products) (or correct cycle) 1 ∆Hc ο (CH3OH) = ∆Hc ο (CO) + 2 × ∆Hc ο (H2) – ∆H 1 = (–283) + (2 × –286) – (–91) (mark for previous equation or this) = –764 (kJ mol–1 ) ( units not essential but lose mark if units wrong) 1 (note + 764 scores 1/3) This is the answer but i am not understanding why they used Ein-Eout .In the book it says DeltaH=products-reactants.Pls clear this confusion
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Updated: January 27, 2018
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