Homework Assignment #1 Intermolecular Forces and Liquids and Solids (Due date: F
ID: 1084991 • Letter: H
Question
Homework Assignment #1 Intermolecular Forces and Liquids and Solids (Due date: February 14th, 2018) 1) List the types of intermolecular forces that exist between molecules (or basic units) in cach of the following species: a) Sodium chloride (NaCI) b) Chloroform (CHCI) c) Methane (CH:) 2) Arrange the following substances in order of increasing boiling point: CH,O1H, He, CHiCI, and NaC) Explain your reasoning. 3) The phase diagram of sulfur is shown below. Monoclinic and rhombic are two allotropes of sulfur. 154 C 1288 atm Liquid Monoclinic Rhombic 10 atm 10 atm Vapor 119°C r CC) 95.4 Using the given phase diagram of sulfur, answer the following questions a) How many triple points are in the diagram? b) Is any critical point shown in the diagram? c) Under atmospheric conditions, which allotrope, the monoclinic or the rhombic, is more stable? .0. Assuming 4) The distance between layers in a sodium chloride (NaCl) crystal is 282 pm that n-1, calculate the wavelength of the X rays in nm (nanometers) . X ray are diffracted from these layers at an angle of 30 ty of 12.02 g/cm and unit cell edge length of 388.9 pm. The Palladium atoms occupy only the lattice points, (a) In t cell, does palladium crystallize? (b) What is the atomic radius of palladium? (Show your calculations step by step) what cubic unit 6) The vapor pressure of propane, CHs, is 40. mmHg at 7.6 °C. What is its pressure at 60.6 C The molar heat of vaporization of propane is 15.7 kJ/mol.Explanation / Answer
1 a) NaCl is an ionic compound. The intermolecular forces in this type of compounds are coulomb interactions. These are produced between a cation with positive charge (Na+ in this case) and an anion with negative charge (Cl-
1 b) CH3Cl is formed by two atoms (C and H) with low electronegativity and one atom (Cl) with high electronegativity. The Cl can attract the electronic cloud near itself. This produce a dipole. So that, the intermolecular forces in this case are dipole-dipole.
1 c) CH4 is this case both H and C have very low electronegativity. So, its molecule is not a dipole. The interaction forces of this molecule are dispersion.
So that, the correct order is,
He < CH3Cl < CH3OH < NaCl
The He is a noble gas. The intermolecular forces in the noble gases are dispersion. This type of forces are the weakest.
The CH3Cl present dipole-dipole interactions. These forces are stronger than the dispersion forces but weaker than the hydrogen bond forces. The hydrogen bond forces are presented in the CH3OH. The hydrogen bond forces are produced between the oxygen of a hydroxyl group and a H of another hydroxyl group.
In the NaCl, the coulomb interactions are presented. These type of interactions are the strongest intermolecular forces.
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