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Example Questions
Example Question #4 : Structure Of Ionic Solids
Zinc Sulfide can be described as a cubic close packed arrangement of Zn with sulfur occupying one-half of the tetrahedral holes. Based upon that description and the figure above, what is the formula for zinc sulfide?
Zn2S
ZnS2
Zn12S4
Zn3S
ZnS
ZnS
The figure above has 8 Zn atoms on the corners (counting as 1/8) and 6 Zn atoms on the faces (counting as ½). This gives 4 Zn atoms in the unit cell. The Sulfur atoms are completely within the unit cell and count as 1 each for a total of 4 S atoms. This gives the formula Zn4S4 which reduces down to ZnS.
Example Question #5 : Structure Of Ionic Solids
What are the names of the alloy types shown in the figure above:
A = Pure Metal; B = Interstitial; C = Substitutional
A = Interstitial; B = Pure metal; C = Substitutional
A = Substitutional; B = Interstitial; C = Pure Metal
A = Pure Meta; B = Substitutional; C = Interstitial
None of the above
A = Pure Meta; B = Substitutional; C = Interstitial
An interstitial alloy has a smaller atom inserted into the unit cell, a substitutional alloy has another atom substitute for the main element, and a pure metal is only composed of a single atom type.
Example Question #1 : Deviations From Ideal Gas Law
Under which conditions would you expect Ar to deviate the most from ideal behavior?
Ar always behaves ideally
200 K and 10 atm
200 K and 1 atm
300K and 10 atm
300K and 5 atm
200 K and 10 atm
The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. At 200K (lowest temperature in the list, and the highest pressure). This gives Ar the most time to interact due to molecular speeds and the high pressure implies the molecular size is not insignificant relative to the container.
Example Question #2 : Deviations From Ideal Gas Law
Would you expect a polar or non polar gas to deviate most from ideal gas behavior?
Non polar gases, because of high dispersion interactions
Non polar gases because of reduced overall intermolecular forces
Polar gases because of hydrogen bonding
Both polar and non polar gases behave ideally
Polar gases, because of high dipole-dipole interactions
Polar gases, because of high dipole-dipole interactions
Polar gases would have increased interactions due to their dipoles that would lead to deviations from ideal gas behavior.
Example Question #3 : Deviations From Ideal Gas Law
Which of the following would behave most like an ideal gas?
All are ideal gases because they are non-polar
Example Question #4 : Deviations From Ideal Gas Law
Why do gases deviate from ideal behavior as the temperature is decreased?
As the temperature is decreased the molecules have less kinetic energy and can’t maintain the intermolecular forces necessary for ideal gas behavior.
None of the above.
As the temperature is decreased the molecules have less kinetic energy and can’t break the intermolecular interactions between them.
As the temperatures is decreased the molecules become frozen in place.
As the temperature is decreased the molecules have more kinetic energy and break the intermolecular interactions keeping them together.
As the temperature is decreased the molecules have less kinetic energy and can’t break the intermolecular interactions between them.
The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. As the temperature is decreased the gas molecules are moving slower and allow for a greater degree of interaction.
Example Question #5 : Deviations From Ideal Gas Law
When does a gas behave most like an ideal gas?
At high temperature, high volumes, and high intermolecular interactions
At high temperatures, high volume, low intermolecular interactions
At low temperatures, high volume, and low intermolecular interactions
At low volumes, high temperatures, and high intermolecular interactions
At low temperatures, low volume, low intermolecular interactions
At high temperatures, high volume, low intermolecular interactions
The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. At high temperatures the gas molecules are moving fast enough to shorten the time scale for any interactions. At high volumes, the molecular size becomes small relative to the size of the container, and the low interactions mean the molecules act more independently.
Example Question #1 : Representations Of Solutions
Which of these solutions can be separated via chromatography?
A homogeneous solution of organic solvents
B and C
Ethanol and water
None of the above
Soil and water
B and C
Chromatography is the physical separation of components of a mixture. Answers b and c can be separated by chromatography due to their homogeneous nature. The soil and water example would be separated by filtration.
Example Question #2 : Representations Of Solutions
Which of the following would most likely form a homogeneous solution?
Water and benzene (C6H6)
A and B
All would form homogeneous solutions
NH4Cl and water
NaNO3 and octanol (C8H18O)
NH4Cl and water
Like dissolves like. The NH4Cl and water mixture involves an ionic solid and a polar solvent. Examples a and b involve mixing polar/non-polar solvents and ionic and non-polar solvents.
Example Question #3 : Representations Of Solutions
If 50g of NaCl are dissolved in 5 L of water what is the solute and what is the solvent?
They both are solvents because they dissolve into each other
NaCl can not be dissolved in water because NaCl is ionic and water is a polar solvent
NaCl is the solute and H2O is the solvent
NaCl is the solvent and H2O is the solute
Both are solutes since they are mixed together
NaCl is the solute and H2O is the solvent
The solvent is what you the most off. In this case water is the solvent and sodium chloride is the solute.
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