12-atoms at grain boundaries are ------chemically reactive than grains .themselves • less more • equal none 13-A reversible changes in an atomic structure of the metal with a corresponding change in the properties of steel, is called • poly-tropic allotropic critical point none of these 14-What types of bonding would you expected of nylon (primary composed from hydrogen and carbon)? • covalent bonds • van der Waals hydrogen • ionic • 1 and perhaps 2 choices

Which of the following term/s is/are true about tacticity? i. Tacticity affects the degree of crystallinity. ii. Tacticity is a polymer property that occurs as a result of chain length and chain structure. iiI. An isotactic polymer shows greater resistance to dissolve in solvents than its atactic and syndiotactic forms. iv. An atactic polymer is melted at higher temperatures than its isotactic and syndiotactic forms. v. When an isotactic polymer is melted, it shows higher melt viscosity than its atactic and syndiotactic forms. I, II, II, Nand V A I, Ill and V III, VandV NandV

Why are insoluble metal oxides considered base anhydrides? O They react with acids O They react with bases O They do not react O They form hydroxides in water