Question

1. the diagrams to the left represent two allotropes of solid phosphorus. which of the following correctly identifies the allotrope with the higher melting point and explains why? a. allotrope i, because it has p4 molecules with covalent bonds that are stronger than dispersion forces between individual p atoms in allotrope ii. b. allotrope ii, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the p4 molecules in allotrope i. c. allotrope ii, because it has metallic bonding that is stronger than the covalent bonding found in the p4 molecules in allotrope i. d. both allotropes have the same melting point because they both contain phosphorous atoms. 5. the crystal structure of nabr is represented in the diagram at left. which statement correctly compares crystalline nabr(s) to molten nabr(l) in terms of electrical conductivity? a. crystalline nabr contains no freely moving electrons that could conduct an electrical current, whereas electrons can flow freely in molten nabr, which is a good conductor of electricity. b. crystalline nabr and molten nabr both contain ions that are held in fixed positions due to strong electrostatic attractions among the ions, making neither a good electrical conductor. c. crystalline nabr and molten nabr both contain na atoms that transfer electrons to br atoms in a chemical reaction, thus allowing them both to be good conductors of electricity. d. crystalline nabr contains no freely moving electrons to conduct electricity, but molten nabr is composed of freely moving na+ and br- ions, which allows it to be a good conductor of electricity.

Explanation:

4.

Allotrope I consists of $P_4$ molecules with dispersion forces between the molecules. Allotrope II has covalent - bonded network structure. Covalent bonds are much stronger than dispersion forces. Stronger intermolecular or inter - atomic forces lead to higher melting points. So Allotrope II has a higher melting point because its covalent bonds between phosphorus atoms are stronger than the dispersion forces between $P_4$ molecules in Allotrope I.

In crystalline $NaBr$, the ions ($Na^+$ and $Br^-$) are held in fixed positions in the crystal lattice and there are no freely - moving charged particles to conduct electricity. In molten $NaBr$, the ionic bonds are broken and the $Na^+$ and $Br^-$ ions are free to move, which allows it to conduct electricity.

Answer:

B. Allotrope II, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the $P_4$ molecules in allotrope I.

5.