Question

Cuprous oxide (cu2o) is being reduced by hydrogen in a furnace at 1000 k.

a.Write the chemical reaction for the reduction of one mole of cu2o.
b.How much heat is released or absorbed per mole reacted? Give the quantity of heat and state whether heat is evolved (exothermic reaction) or absorbed (endothermic reaction). Data: heats of formation at 1000 k in kj mol−1 : for cu2o = −175.31 kj mol−1 ; for h2o = −247.73 kj mol−1 .

Answer 1

a) The reduction reaction for Cu2O is

Cu2O + H2 ---> 2Cu(s) + H2O

b) the enthalpy of reaction is

ΔHrxn = ∑ΔHformation of products - ∑ΔHformation of reactants

We know that

ΔHformation of elements in their native state = 0 = ΔHf (H2) = ΔHf (Cu)

ΔHrxn = ΔHf (H2O) - ΔHf (Cu2O) = -247.73 - (-175.31) = -72.42 kJ

So as enthalpy of reaction is negative the reaction is exothermic and heat will be evolved during the reaction