Chemistry Quiz Chapter 2

What would be the pressure (in atm) of a 5.00 mol sample of Cl at 400.0 K in a 2.00 L container found using the van der Waals equation? For Cl , a = 6.49 L² atm/mol² and b = 0.0652 L/mol. 57.4 atm Which of the following substances would not exhibit any hydrogen bonding interactions in a pure substance? a) H O b) HF c) N(CH ) d) CH CH OH e) CH NH **Hydrogen bonding results when a hydrogen atom is covalently bonded to the highly electronegative N, O, or F atoms, resulting in a large partial positive charge on the H atom. Since N(CH£)£ is the only option without H bonded directly to N, O, or F (here, there are only C-H bonds), it would not exhibit hydrogen bonding. Which one of the following correctly ranks the compounds in order of lowest enthalpy of vaporization to the highest enthalpy of vaporization based only on intermolecular forces? a) CH NH < CH SH < CH CH b) CH NH < CH CH < CH SH c) CH CH < CH SH < CH NH d) CH SH < CH NH < CH CH **CH£NH¢ would have the most intermolecular forces, with hydrogen bonding, dispersion forces, and dipole-dipole interactions. CH£SH would have the second most intermolecular forces, with dispersion forces and dipole-dipole interactions. CH£CH£ would have the fewest intermolecular forces with only dispersion forces. The stronger the intermolecular forces are, the higher the magnitude of the enthalpy of vaporization will be. Which of the following straight-chain hydrocarbons will have the highest viscosity at 298 K? a) C H b) C H c) C H d) C H e) C H **Viscosity is defined as a liquid's resistance to flowing, so compounds with stronger intermolecular forces will have higher viscosities. Since these options are all nonpolar molecules, C₉H¢₀ , which has the most electrons to be dispersed and therefore the strongest intermolecular forces will have the highest viscosity. Which of the following phase changes is endothermic? a) Sublimation b) Deposition c) Freezing d) Condensation **An endothermic phase change is one that requires the input of energy to overcome intermolecular forces. Of these options, only sublimation requires the input of energy (to escape from the solid to the gas phase), meaning it is endothermic. What amount of heat, in kJ, would be involved in condensing 15.8 g of CH OH? (∆Hvap = 38.0 kJ/mol) -18.7 kJ **Since grams of CH£OH was provided, that will be the starting point, with the molar mass and heat of vaporization (which is negative since condensation is an exothermic process) providing the conversion factors. What is represented by B on the phase diagram? A) solid B) liquid C) gas D) cannot determine without exact pressure and temperature **Point B on this phase diagram falls within a region of high pressure (which will force the substance into a condensed phase) and high temperature (which will take allow this substance to overcome its intermolecular forces). These forces balance to give the moderately condensed liquid phase.