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Given the following thermochemical equation, what amount of energy is absorbed/given off when 255g of Cu2O is reacted:

2Cu2O(s)=4Cu(s)+O2(g)

I just want to make sure I've set it up correctly. :)

Respuesta :

Edufirst
A thermochemical equation must include the heat absorbed or given, so this question is incomplete.


So, I will work with the data of heat of formation from a table.


In this case, the table says:


4 Cu(s) + O2(g) ----> 2 Cu2O (s)    ΔHf = -333.4 kJ/mol


Our equation is in the inverse direction so ΔH'f = - ΔHf = 333.4 kJ/mol


Then, the heat of formation of our reaction is positive, which means that it is endothermic or absorb energy.


So, we know that the thermal equation is:


 2 Cu2O(s) + 333.4 kJ / mol ⇄ 4 Cu(s) + O2(g)


That is, 2 mol Cu2O(s) absorbs 2 * 333.4 kJ   of heat


Now calculate the number of moles of Cu2O in 255 g


You need the molar mass of Cu2O


Cu2O : 2 * 63.5 g/mol + 16 g/mol = 143 g/mol


# moles Cu2O = 255 g / 143 g /mol = 1.78 mol


 => ΔH = 1.78 mol * 333.4 kJ / mol = 593.5 kJ



Answer: 593.5 kJ is absorbed