AP Chemistry : AP Chemistry

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #71 : Compounds And Molecules

04

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?

Possible Answers:

ZnS

ZnS2

Zn2S

Zn3S

Zn12S4

Correct answer:

ZnS

Explanation:

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 #1 : Structure Of Ionic Solids

 05

What are the names of the alloy types shown in the figure above:

Possible Answers:

A = Interstitial; B = Pure metal; C = Substitutional

None of the above

 A = Pure Metal; B = Interstitial; C = Substitutional

A = Substitutional; B = Interstitial; C = Pure Metal

 A = Pure Meta; B = Substitutional; C = Interstitial

Correct answer:

 A = Pure Meta; B = Substitutional; C = Interstitial

Explanation:

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?

Possible Answers:

200 K and 10 atm

300K and 10 atm

300K and 5 atm

200 K and 1 atm

Ar always behaves ideally

Correct answer:

200 K and 10 atm

Explanation:

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 #1 : Deviations From Ideal Gas Law

Would you expect a polar or non polar gas to deviate most from ideal gas behavior?

Possible Answers:

Polar gases, because of high dipole-dipole interactions

Both polar and non polar gases behave ideally

Polar gases because of hydrogen bonding

Non polar gases, because of high dispersion interactions

Non polar gases because of reduced overall intermolecular forces

Correct answer:

Polar gases, because of high dipole-dipole interactions

Explanation:

Polar gases would have increased interactions due to their dipoles that would lead to deviations from ideal gas behavior.

Example Question #101 : Solutions And States Of Matter

Which of the following would behave most like an ideal gas?

Possible Answers:

 in 10 L

 in 10 L

 in 10 L

 in 10 L

All are ideal gases because they are non-polar

Correct answer:

 in 10 L

Explanation:

 is the smallest molecule in the list, and therefore the least size effects.

Example Question #102 : Solutions And States Of Matter

Why do gases deviate from ideal behavior as the temperature is decreased?

Possible Answers:

As the temperatures is decreased the molecules become frozen in place.

None of the above.

As the temperature is decreased the molecules have less kinetic energy and can’t maintain the intermolecular forces necessary for ideal gas behavior.

As the temperature is decreased the molecules have less kinetic energy and can’t break the intermolecular interactions between them.

As the temperature is decreased the molecules have more kinetic energy and break the intermolecular interactions keeping them together.

Correct answer:

As the temperature is decreased the molecules have less kinetic energy and can’t break the intermolecular interactions between them.

Explanation:

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 #621 : Ap Chemistry

When does a gas behave most like an ideal gas?

Possible Answers:

At low temperatures, low volume, low 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 high temperature, high volumes, and high intermolecular interactions

Correct answer:

At high temperatures, high volume, low intermolecular interactions

Explanation:

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?

Possible Answers:

Soil and water

B and C

None of the above

A homogeneous solution of organic solvents

Ethanol and water

Correct answer:

B and C

Explanation:

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?

Possible Answers:

Water and benzene (C6H6)

All would form homogeneous solutions

NaNO3 and octanol (C8H18O)

NH4Cl and water

A and B

Correct answer:

NH4Cl and water

Explanation:

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 #1 : Representations Of Solutions

If 50g of NaCl are dissolved in 5 L of water what is the solute and what is the solvent?

Possible Answers:

NaCl can not be dissolved in water because NaCl is ionic and water is a polar solvent

NaCl is the solvent and H2O is the solute

They both are solvents because they dissolve into each other

Both are solutes since they are mixed together

NaCl is the solute and H2O is the solvent

Correct answer:

NaCl is the solute and H2O is the solvent

Explanation:

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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