���______ pts. out of 100 possible pts. = _______ % =����������������������������� Name:

 

Advanced Chemistry:� Test #5 (Interparticle Forces & Phase Changes)

 

Multiple Choice:� Circle the letter to the left of the best answer.� (Questions 1-21 are 2 pts. each)

 

1.����� If molecule X has weaker intermolecular forces than molecule Y then:

 

  1. X will have a higher vapor pressure and a lower boiling point than Y.
  2. Y will have a higher vapor pressure and a lower boiling point than X.
  3. X will have a higher vapor pressure and a higher boiling point than Y.
  4. Y will have a higher vapor pressure and a higher boiling point than X.
  5. X will have a higher vapor pressure and a higher heat of vaporization than Y.

 

  1. Which of the following has the lowest vapor pressure?

 

  1. SiC
  2. CO2
  3. H2O
  4. HCl��
  5. HF

 

  1. A certain solid has a melting point of 80.oC.� It is soluble in water and the resulting solution does not conduct electricity.  This solid is most likely:

 

  1. a polar molecular solid
  2. a metal
  3. ionic
  4. a macromolecular solid
  5. a nonpolar molecular solid

 

  1. The temperature at which a solid is in dynamic equilibrium with the liquid of that same substance is known as its:

 

  1. boiling point
  2. melting point
  3. heat of fusion
  4. heat of vaporization
  5. critical point

 

5.� The energy involved in melting a substance is called its:

 

  1. boiling point
  2. melting point
  3. heat of fusion
  4. heat of vaporization
  5. heat of sublimation

 

  1. If five molecules all have about the same molecular weight, the one with the lowest vapor pressure will be the:

 

  1. metallic solid
  2. ionic solid
  3. covalent network solid
  4. nonpolar molecular solid
  5. polar molecular solid

 

 

  1. Which of the following pairs of solids are both held together by hydrogen bonds?

 

  1. H2O and CH4
  2. NH3 and HF
  3. H2 and CH4
  4. H2O and HI
  5. NH3 and CH4

 

  1. Which of the following solids is not held together by London forces?

 

  1. H2
  2. I2
  3. CH4
  4. CO2
  5. SO2

 

  1. A certain solid has a melting point of 800.oC and it does not conduct electricity.� It is soluble in water and the resulting solution conducts electricity.  This solid is most likely:

 

  1. a polar molecular solid
  2. a metal
  3. ionic
  4. a macromolecular solid
  5. a nonpolar molecular solid

 

  1. A sealed container is half filled with water, all the gas above the liquid has been removed by a vacuum pump, and the container has been resealed.� Some of the water then evaporates until an equilibrium vapor pressure of 75 mmHg is reached at a temperature of 50oC.� To increase the vapor pressure you could:

 

  1. add more water
  2. decrease the temperature
  3. reduce the volume of the container
  4. more than one of the above
  5. none of the above

 

  1. Calcium is:

 

  1. a metallic solid
  2. an ionic solid
  3. a covalent network solid
  4. a nonpolar molecular solid
  5. a polar molecular solid

 

  1. SeS2 is:

 

  1. a metallic solid
  2. an ionic solid
  3. a covalent network solid
  4. a nonpolar molecular solid
  5. a polar molecular solid

 

 

 

 

 

  1. Silicon dioxide is:

 

  1. a metallic solid
  2. an ionic solid
  3. a covalent network solid
  4. a nonpolar molecular solid
  5. a polar molecular solid

 

  1. Strontium fluoride is:

 

  1. a metallic solid
  2. an ionic solid
  3. a covalent network solid
  4. a nonpolar molecular solid
  5. a polar molecular solid

 

  1. Phosphorus tribromide is:

 

  1. a metallic solid
  2. an ionic solid
  3. a covalent network solid
  4. a nonpolar molecular solid
  5. a polar molecular solid

 

 

 

 

Questions 16-21 refer to the phase diagram above and to the substance that the diagram represents.

 

 

  1. The arrow in the diagram is pointing to the:

 

 

 

 

  1. The normal melting point for the substance represented by the diagram is about:

 

 

  1. The normal boiling point for the substance represented by the diagram is about:

 

 

  1. The critical temperature for the substance represented by the diagram is about:

 

 

  1. If you were to place a solid piece of the substance (represented by the diagram) on your desk right now, it would:

 

  1. melt
  2. sublime
  3. remain a solid
  4. melt and then boil
  5. be in equilibrium with the liquid phase

 

  1. Which of the following statements is true concerning the substance represented by the phase diagram?

 

  1. The liquid can be converted into a gas without changing the temperature by increasing the pressure.
  2. The liquid can be converted into a solid without changing the temperature by increasing the pressure.
  3. The solid can be converted into a gas without changing the temperature by increasing the pressure.
  4. The solid can be converted into a liquid without changing the temperature by increasing the pressure.
  5. None of the above statements is true.

 

 

 

  1. Draw a heating curve starting at 50. K and ending at 450. K for the substance represented by the phase diagram on the previous page.  Label each section of the curve to show what state or states are present.�� (4 pts.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. Draw 2 different molecules that are attracted to each other by hydrogen bonding.� Neither molecule can be water.� Draw an arrow that points to the hydrogen bond.� (2 pts.)

 

 

 

 

 

 

 

 

 

 

  1. Identify the following as metallic, ionic, polar molecular, nonpolar molecular, or macromolecular (covalent network) solids: �( 10 pts.)

 

����������������������� a) CS2                      ������������������ ���������������� b) U

 

����������������������� c) MgO                      ���������������� ���������������� d) SeS2

 

����������������������� e) H2S                   ��������������������� ���������������� f) SiC

 

����������������������� g)  Co��������������������������������������������������������� h)� AsBr3

 

����������������������� i)� SiO2�������������������������������������������������������� j)� KF

 

 

  1. List the order of the strength of the following from strongest to weakest (list using the associated letter):� (3 pts.)

����������������

��������� A) dipole-dipole attractions���� B) covalent bonds���� C) London forces

���������������� D) hydrogen bonds���� E) ionic bonds

 

 

 

26.���� Circle the compound in each of the following pairs that meets the description given, and explain your answer in one or two sentences.� (3 pts. each)

 

����������������������� a) the highest boiling point: C3H8 or C5H12

 

 

 

 

 

 

����������������������� b) the highest vapor pressure:� HCl or HBr

 

 

 

 

 

 

����������������������� c) the highest vapor pressure: H2O or HCl

 

 

 

 

 

����������������������� d) the highest melting point: MgO or CaO

 

 

 

 

 

 

����������������������� e) the highest melting point: MgO or NaF

 

 

 

 

 

 

����������������������� f) the highest heat of vaporization: SeCl6 or SeCl4

 

 

 

 

 

 

����������������������� g) the highest boiling point: SeCl2 or TeCl2

 

 

 

 

 

 

����������������������� h) the lowest vapor pressure: CO2 or CS2

 

 

 

 

 

 

����������������������� i) the lowest melting point: NH3 or NF3

 

 

 

 

 

 

 

����������������������� j) the higher melting point:� NF3 or PF3

 

 

 

 

 

 

����������������������� k)� the higher vapor pressure:� SiO2� or� SO2

 

 

 

 

  1. How much energy is needed to vaporize a 35.0 g piece of copper that is initially at room temperature?� (6 pts.)

(The specific heat of liquid copper is 0.493 J/g.oC.)