Challenging Chem

2007-07-08 10:48 pm

Mixing household cleansers can result in the production of HCl (g). Not only is this gas dangerous in its own right, but it also reacts with oxygen to form chlorine gas and water vapour.
4HCl (g) + O2 (g) to 2Cl2 (g) + 2H2O (g)

更新1:

Determine the enthalpy change of this reaction, given the following equations: 1. H2 ( g)+Cl2 (g ) to 2HCl (g ) delta H = -185kJ 2. H2 (g )+ 1/2 O2 to H2O ( l) delta H = -285.8kJ 3. H2O (g ) to H2O (l ) delta H = -40.7kJ

回答 (2)

魏王將張遼

2007-07-09 3:57 am

✔ 最佳答案

As follows:

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參考: My chemical knowledge

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2007-07-08 11:04 pm

on left hand side,
enthalpy of formation of 4HCl(g) = -185kJ x 2= -370kJ

on right hand side,
enthalpy of formation of 2H2O(l) = -285.8 x 2 = -571.6kJ
2H2O(l) to 2H2O(g) = +40.7kJ x 2 = 81.4 kJ
formation of 2H2O(g) = -571.6 + 81.4 = - 490.2kJ

enthalpy change = -490.2 - (-370) = -120.2kJ/mol

the system lose energy. energy released as heat (exothermic)

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