CHEM125 – CHAPTER 11 – REGULAR HOMEWORK

CHAPTER 11 REGULAR HOMEWORK

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Question 1

Referring to the figure below, match the letter with the phase of the substance. ALL MUST BE CORRECT TO GET CREDIT.
CHEM125 - CHAPTER 11 - REGULAR HOMEWORK 1
G Correct
H Correct
J Correct
K Correct

Explanation

Triple Point – where all 3 states exist

Question 2

Check the 2 statements which are correct.
Select one or more:
 Correct
 Correct

Explanation

Trace the line above in the graph

Question 3

Identify the kinds of intermolecular forces (London dispersion, dipole-dipole, hydrogen bonding) that are the most important for methane (CH4).
Select one:
 Correct

Explanation

  • Dispersion forces are present for all molecules
  • Nonpolar so no dipole forces
  • No hydrogen bond

Question 4

Identify the kinds of intermolecular forces that are the most important for methanol (CH3OH).
Select one:

Explanation

  • Hydrogen Bond most strongest bond type (hydrogen bond with only, F, O, N)
  • Dispersion forces present for all molecules but not most important

Question 5

Identify the kinds of intermolecular forces that are the most important for chloroform (CHCl3).
Select one:

Explanation

  • Dispersion Forces are present for all molecules
  • Polar so dipole forces present
  • No hydrogen bond present

Question 6

Identify the kinds of intermolecular forces that are the most important for benzene (C6H6).
Select one:
 Correct

Explanation

  • Dispersion Forces are present for all molecules
  • Nonpolar so no dipole forces
  • No hydrogen bond present

Question 7

Identify the kinds of intermolecular forces that are the most important for ammonia (NH3).
Select one:
 Correct

Explanation

  • Hydrogen Bond most strongest bond type (hydrogen bond with only, F, O, N)
  • Dispersion forces present for all molecules but not most important

Question 8

Identify the kinds of intermolecular forces that are the most important for sulfur dioxide (SO2).
Select one:

Explanation

  • Dispersion Forces are present for all molecules
  • Polar so dipole forces present
  • No hydrogen bond present

Question 9

In each part, select the substance that has the higher boiling point, based on the relative strengths of the intermolecular attractions.
Select one or more:
 Correct
 Correct
 Correct
 Correct
 Correct

Explanation

Dispersion force increases with increase in molar mass.
CHEM125 - CHAPTER 11 - REGULAR HOMEWORK 2

Question 10

Select the liquid in each part that has the greater expected enthalpy of vaporization.
Select one or more:
 Correct
 Correct
 Correct
 Correct
 Correct

Explanation

  • Enthalpy of vaporization increases with molar mass
  • Enthalpy of hydrogen bond is the greatest

Question 11

Identify the kinds of forces that are most important in holding the particles together in a crystalline solid sample of Kr.
Select one:
 Correct

Explanation

  • All elements have dispersion force
  • Kr is not polar
  • Kr does not have a hydrogen bond

Question 12

Identify the kinds of forces that are most important in holding the particles together in a crystalline solid sample of HF.
Select one:
 Correct

Explanation

  • Hydrogen Bond most strongest bond type (hydrogen bond with only, F, O, N)
  • Dispersion forces present for all molecules but not most important

Question 13

Identify the kinds of forces that are most important in holding the particles together in a crystalline solid sample of K2O.
Select one:
 Correct

Explanation

  • Ionic bond is stronger than hydrogen bond
CHEM125 - CHAPTER 11 - REGULAR HOMEWORK 2

Question 14

Identify the kinds of forces that are most important in holding the particles together in a crystalline solid sample of CO2.
Select one:
 Correct

Explanation

  • Dispersion Forces are present for all molecules
  • Nonpolar so no dipole forces
  • No hydrogen bond present

Question 15

Identify the kinds of forces that are most important in holding the particles together in a crystalline solid sample of Zn.
Select one:
 Correct

Explanation

  • Zn is a metal so makes metallic bond

Question 16

Identify the kinds of forces that are most important in holding the particles together in a crystalline solid sample of NH3.
Select one:
 Correct

Explanation

  • Hydrogen Bond most strongest bond type (hydrogen bond with only, F, O, N)
  • Dispersion forces present for all molecules but not most important

Question 17

Correlate the properties below with each of these substances.
N2O
GeO2
CaCl2

Explanation

N2O does not conduct electrical current because nonmetal GeO2 does not conduct electrical current because nonmetal CaCl2 ionic bond conducts electricity

Question 18

A 1.50 g sample of methanol (CH3OH) is placed in an evacuated 1.00 L container at 30. oC. Calculate the pressure (in torr) in the container if all of the methanol is vaporized. (Assume the ideal gas law, PV = nRT).
Correct

Explanation

1.50g CH3OH / (32 g/mol CH3OH) = 0.4687 mol CH3OH PV = nRT P = nRT/V = (.046875)(0.08206)(303) / 1 = 1.165 atm 1.165 atm x (760 torr/ 1atm) = 885 torr

Question 19

The vapor pressure of methanol at 30. oC is 158 torr. What mass (in grams) of methanol actually evaporates? Aside (don’t answer), is the liquid in equilibrium with vapor in the vessel?
Correct

Explanation

PV = nRT 158 torr = 0.20789 atm n = PV / RT = (.20789 atm x 1 L) / (.08206 x 303K) = .00836 mol .00836 mol x 32 g/mol = 0.267 g

Question 20

How much heat is absorbed by a 25.0 g sample of water in going from liquid at 26.7 oC to steam at 137 oC and a pressure of 1.00 atm? Use the data in the following table . Express your answer in kilojoules. Pay attention to units!
 Correct

Explanation

ΔH = heat raise temp to 100 C + heat vaporisation + heat increase temperature to 137C ΔH = mcΔt + mL + mCΔt ΔH = (29.8*(4.18)*(100-26.7)) + ((29.8/18)*40.6*1000) + (25*2.01*(137 – 100)) ΔH = 7733 + 56390 +1859 ΔH = 65.8 kJ