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CHAPTER 11 BASIC HOMEWORK:

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Question 1

Correctly match the properties. 

Help: Energy of attraction

Water at -50oC Correct
Water at 50oC Correct
Water at 150oC Correct

 

Explanation

At below freezing point the kinetic energy of molecules is very minimum.


At 50 C the kinetic energy of molecules is equal to the attraction of the molecules.


At 120 C  the kinetic energy of molecules is greater than the attraction of the molecules.

 

Question 2

Which of the following molecules have dipole-dipole forces between different molecules? (The question is equivalent to asking which of the following molecules are polar molecules. Lewis structures may need to be drawn.) 


Select one or more:
 Correct
 Correct
 Correct

 

Explanation

Dipole–dipole force exists between all molecules that are polar. Polar molecules have electron-rich regions (which have a partial negative charge) and electron-deficient regions (which have a partial positive charge).


 

Question 3

Which of the following molecules have H-bonding and thus a higher than expected melting and boiling point?

Help: Hydrogen bonding

Select one or more:
 Correct
 Correct
 Correct

 

Explanation

H bonds occur between with only these elements F, O, N

 

Question 4

For each of the following molecules pick the one with the greater London forces and hence higher melting and boiling point? 

Help: London forces

Select one or more:

 Correct
 Correct
 Correct
 Correct

 

Explanation

Dispersion forces are the result of fluctuations in the electron distribution within molecules or atoms.

 

Question 5

What is the greatest contribution to the energy of interaction between different water molecules.

Help: Energy of interaction

Select one:
 Correct

 

Explanation

Hydrogen Bonding is the strongest among dispersion (London) , dipoles forces.

 

Question 6

What is the greatest contribution to the energy of interaction between different Ar atoms.

Select one:
 Correct

 

Explanation

London forces are the result of fluctuations in the electron distribution within molecules or atoms.

 

Question 7

What is the greatest contribution to the energy of interaction between different ammonia, NH3, molecules.


Select one:
 Correct

 

Explanation

  • Dispersion (london ) forces are present 
  • Hydrogen bond is present with N (this is a greater contributor to the energy of interaction between different molecules)

 

Question 8

Arrange the following molecules from smallest to greatest London forces: Br2, Cl2, and I2

For Br2, Cl2, I2 write Br2, Cl2, I2 or Br2 Cl2 I2

Help: Polarizability

 

Explanation

Dispersion force increases with increasing molar mass because molecules or
atoms of higher molar mass generally have more electrons dispersed over a greater volume.

 

Question 9

Arrange the following molecules from lowest to highest melting point temperature: Br2, Cl2, and I2.

 

Explanation

Dispersion force increases with increasing molar mass because molecules or
atoms of higher molar mass generally have more electrons dispersed over a greater volume.


Greater the dispersion force the stronger the intermolecular force. This means higher melting point

 

Question 10

In the series CH4, SiH4, GeH4, and SnH4, the boiling point increases

Select one:
 Correct

 

Explanation

Dispersion force increases with increasing molar mass because molecules or
atoms of higher molar mass generally have more electrons dispersed over a greater volume.


Greater the dispersion force the stronger the intermolecular force. This means higher melting point

 

Question 11

Why do water, hydrogen fluoride, and ammonia have unusually high boiling points? Due to

Select one:
 Correct

 

Explanation

Hydrogen Bonding is the strongest among dispersion (London) , dipoles forces.

 

Question 12

All but one of the following statement is true. Using your everyday experience, check the false one.

Select one:
 Correct

 

Explanation

If the cup is sealed the vapor pressure can not rise easily to break the glass

 

Question 13

Which of the following statements are true about evaporation for a liquid? 

Help: Evaporation

Select one or more:
 Correct
 Correct
 Correct

 

Explanation

  • Only the most energetic molecules evaporate.
 

Question 14

At what temperature is the equilibrium vapor pressure of water about 100 torr?

Select one:
 Correct

 

Explanation

JUST LOOK AT THE GRAPH

 

Question 15

At what temperature is the equilibrium vapor pressure of water about 400 torr?

Select one:
 Correct

 

Explanation

JUST LOOK AT THE GRAPH ABOVE

 

Question 16

If atmospheric pressure were 600 torr, at what temperature would water boiling? 
Select one:
 Correct

 

Explanation

JUST LOOK AT THE GRAPH ABOVE

 

Question 17

Would ethanol at 80oC boil, if atmospheric pressure were 900 torr?

Select one:
 Correct

 

Explanation

JUST LOOK AT THE GRAPH ABOVE

 

Question 18

A solid melts at -50oC and boils at 75oC. What happens when heat is added to the solid at -80oC?

Help: Heat transfer

Select one:
 Correct

 

Explanation

The temperature of the solid keeps on increasing without phase changing  until the it reaches the melting point at -50oC

 

Question 19

What happens when heat is added to the solid at -50oC?

Select one:
 Correct

 

Explanation

The solid melts at the melting point of -50oC  but the temperature remains the same.

 

Question 20

What happens when heat is added to the liquid at 75oC?

Select one:
 Correct

 

Explanation

The liquid will boil at the boiling point of 75oC but the temperature remains the same.

 

Question 21

Suppose food is cooked in boiling water, using just enough heat to keep the water boiling. Would the food cook faster, if the heat were turned on high? Why? (Pick 2 answers.)

Select one or more:
 Correct
 Correct

 

Explanation

Once water reaches its boiling point the adding more heat will make it boil faster and evaporate faster. The temperature of the water will not change, instead water will  go through as phase change from liquid to gas. 

 

Question 22

Water exists as a solid, liquid, or gas? At 0.5 atm and -5oC, what is the phase?

Select one:
 Correct

 

Explanation

 

Question 23

At 1 torr and 0.01oC, what is the phase?

Select one:
 Correct

 

Explanation

Look at the graph above

 

Question 24

At what temperature does water boil at 0.5 atm? 
Select one:
 Correct

 

Explanation

Look at the graph above

 

Question 25

Check the correct statements about carbon dioxide. 

Select one or more:
 Correct
 Correct
 Correct
 Correct

 

Explanation

Look at the Graph


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