2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/79026We prove that it is consistent that there is a non-reflexive Whitehead group, in fact one whose dual group is free. We also prove that it is consistent that there is a group A such that Ext(A,Z) is torsion and Hom(A,Z)=0. As an application we show the consistency of the existence of new co-Moore spaces.LogicCommutative AlgebraRings and AlgebrasPrimary 20K35, 20K20, 03E35, 03E75; Secondary 13L05, 18G15, 55N10text