Iron oxide concretions, commonly found in sedimentary rocks such as sandstone, are not typically magnetic. These geological phenomena form when mineral cement, mainly iron oxide, precipitates and hardens around a nucleus within rock layers, creating a distinct, often spherical, shape. The most common forms of iron oxide present in concretions are hematite (Fe2O3) and goethite (FeO(OH)), neither of which are strongly magnetic. However, if the iron oxide is in the form of magnetite (Fe3O4), the concretion can exhibit magnetic properties. The presence and concentration of magnetite within an iron oxide concretion would therefore determine its magnetic behavior. In general, while some iron oxide concretions could be weakly magnetic due to minor magnetite content, the majority are not significantly attracted to a magnet.

Acrylonitrile (C3H3N) can be synthesized through the Sohio process, which involves the catalytic ammoxidation of propylene. The reaction is as follows: C3H6 + NH3 + 3/2 O2 → C3H3N + 3 H2O. Assuming 100% yield, the mass of acrylonitrile produced depends on the molar masses of the reactants and the stoichiometry of the reaction. Propylene (C3H6) has a molar mass of 42.08 g/mol, NH3 has a molar mass of 17.03 g/mol, and acrylonitrile has a molar mass of 53.06 g/mol. For simplification, if one mole of propylene (42.08 g) is used, theoretically, one mole of acrylonitrile (53.06 g) is produced at 100% yield. This is under ideal conditions, not accounting for practical limitations such as incomplete reactions, side reactions, or process losses.

Loosening PVC cement, once it has cured, is notoriously difficult because the cement chemically fuses the PVC materials together, creating a permanent bond. In essence, the pieces are no longer separate but have become one. However, if you need to separate PVC pipes or fittings after the cement has set, you might have limited options. Heating the joint with a heat gun or hair dryer can sometimes soften the PVC enough to allow some manipulation, but caution is required to avoid damaging the material or causing injury. Cutting the PVC is often the most viable option, using a saw or pipe cutter, and then replacing the affected section. Always ensure safety measures are in place, including wearing protective gear and working in a well-ventilated area.