AP Chemistry Exam studyguide
The diagrams above represent two allotropes of solid phosphorus. Which of the following correctly identifies the allotrope with the higher melting point and explains why?
Allotrope IIII, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the P4P4 molecules in allotrope II.
The crystal structure of NaBr is represented in the diagram above. Which statement correctly compares crystalline NaBr(s) to molten NaBr(l) in terms of electrical conductivity?
Crystalline NaBrNaBr contains no freely moving electrons to conduct electricity, but molten NaBrNaBr is composed of freely moving Na+Na+ and Br−Br− ions, which allows it to be a good conductor of electricity. Correct. In crystalline NaBrNaBr, there are no free electrons (or any other charged particles) that can move to carry an electrical current. But when molten, NaBrNaBr has freely moving ions that can carry an electric current.
Which particle diagram shown above best represents the strongest intermolecular force between two ethanol, C2H6O, molecules?
Diagram 2, because it shows the formation of a hydrogen bond between an HH atom bonded to an OO atom with an OO atom from another molecule.
The diagram above represents four cations, all shown to the same scale. Which cation would be predicted by Coulomb's law to have the strongest ion-dipole attraction to water, and why?
Mg2+Mg2+ , because it has the largest charge-to-size ratio.