Concept explainers
Determine the number of protons and electrons in each of the following ions:
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Chemistry In Focus
- CaTiO3 has a perovskite structure. Calculate the packing factor.Data: ionic radii Co+2 = 0.106 nm, Ti+4 = 0.064 nm, O-2 = 0.132 nm; lattice constant is a = 2(rTi4+ + rO-2).(a) 0.581(b) -0.581(c) 0.254(d) -0.254arrow_forwardIn the initial linear section of the stress-strain curve of a metal or alloy. Explain from the point of view of atomic structure?(a) No, the atomic level properties of the material can never be related to the linear section.(b) The elastic zone is influenced by the strength of the bonds between atoms.(c) The stronger the bond, the less rigid and the lower the Young's Modulus of the material tested.(d) The stronger the bond, the less stress is necessary to apply to the material to deform it elastically.arrow_forwardThe degree of polymerization of polytetrafluoroethylene (Teflon) is 7500 (mers/mol). If all polymer chains have equal length, state the molecular weight of the polymer and the total number of chains in 1000 g of the polymer(a) 50 000 g/mol; 0.03·1020 chains(b) 100 000 g/mol; 1.03·1020 chains(c) 750 000 g/mol; 8.03·1020 chainsarrow_forward
- In natural rubber or polyisoprene, the trans isomer leads to a higher degree of crystallinity and density than the cis isomer of the same polymer, because(a) it is more symmetrical and regular.(b) it is less symmetrical.(c) it is irregular.arrow_forwardMost ceramic materials have low thermal conductivities because:(a) Electron mobility is strongly restricted due to their strong ionic-covalent bonding.(b) False, in general they are excellent thermal conductors (they are used in ovens).(c) Electron mobility is dependent on T and therefore they are poor conductors at high temperatures.(d) Electron mobility is very restricted by secondary bonds.arrow_forwardResistivity and electrical conductivity.(a) In metals, resistivity decreases.(b) In metals, resistivity decreases and conductivity in semiconductors also decreases with increasing temperature.(c) With increasing temperature, resistivity in metals and conductivity in semiconductors also increases.(d) None of the above.arrow_forward
- State the difference between concrete and Portland cement.(a) There are no differences, in concrete the chemical composition is silicates and in cement aluminates.(b) The chemical composition of concrete is based on silicates and in cement aluminates.(c) Concrete is composed of aggregates bound by cement and cement "only" contains different minerals.(d) Cement is aggregates bound by concrete.arrow_forwardAmorphous polymers are usually transparent and semi-crystalline polymers are usually opaque. Correct?(a) No. They are all made up of polymer chains. True if they were monomers.(b) Yes. The arrangement of the chains determines the passage of light.(c) No. It is the other way around.(d) Crystallinity or amorphousness does not affect the transparency or opacity of the material.arrow_forwardThe name ferrites refers to a family of(a) ceramic materials that exhibit ferrimagnetic behavior due to their ionic composition.(b) polymeric materials that exhibit ferrimagnetic behavior due to their ionic composition.(c) concrete-based materials that exhibit ferrimagnetic behavior due to their ionic composition.(d) superconducting materials that exhibit ferrimagnetic behavior due to their ionic composition.arrow_forward
- State the two main factors affecting ion packing in the solid state.(a) Number of covalent bonds and their unsaturation.(b) Mechanical properties and degradation temperature.(c) Number of crystalline phases present and grain size.(d) Electroneutrality and ion size.arrow_forwardThe ceramic materials alumina (Al2O3) and chromium oxide (Cr2O3) form an isomorphic phase diagram. The solubility will be(a) unlimited of one ceramic in the other.(b) very limited depending on the weight % of Al2O3(c) very limited depending on the weight % of Cr2O3(d) partial of one ceramic in the other.arrow_forwardAmong the main characteristics of optical fibers, indicate which of the following is not included:(a) Opacity and Rigidity(b) Flexibility(c) Transparency(d) Low thicknessarrow_forward