The oxidation of copper(I) oxide,
Cu2O(s), to copper(II) oxide, CuO(s), is an exothermic
2 CuO2(s) + 02(g) —> 4 CuO (s)
The change in enthalpy upon reaction of 67.68 g of CuO (s) is
Calculate the work, w, and the energy change, delta Urxn, when
67.68 g of Cu2O (s) is oxidized at constant pressure of 1.00 bar
and a constant temperature of 25 degree celcius?
(the two answer must be in kJ)
I can’t get the right answer for some reason.
Show work please.
classmAte Date Page Mo 143-) PAo eik ニー587-18 /Tou
The balanced chemical reaction is :
O (s) + O2
(g) ————-> 4CuO
given that 67.68 g of Cu2
O is reacted i.e.
number of moles of Cu2
O reacted = 67.68 g / 143.1 g
= 0.473 mol
The stoichiometry of the balanced equation tells that each 2 mol
O reacts with 1 mole of O2
number of moles of O2
reacted = 0.473 / 2 = 0.24
change in number of moles (Δn) of the compound in the gaseous
state in the reaction is :
Δn = nproducts (g)
= 0 – 0.24
and work done in chemical reaction given by
w = – ΔnRT
= – (-0.24 mol) * 8.314 J K-1
= 594.62 J
~= 0.594 kJ which is actually expansion (compression) work
positive sign indicates that work is done on the system.
Also, ΔH = ΔU + Δ(PV)
at constant pressure,
ΔH = ΔU + PΔV
=> ΔU = ΔH – PΔV
= -69.06 – 0.59
~= -69.65 kJ