GEN CHEM 2

Which of the following best explains water's ability to dissolve certain substances such as glucose, but remain separate from other substances such as oils?

• Due to hydrogen bonding, water is more dense as a liquid than a solid.

• Water molecules can form ionic bonds with polar molecules, such as glucose.

• Water has an overall negative charge, which allows it to easily dissolve nonpolar substances like glucose.

• Water molecules are polar, consisting of two partially positive hydrogen atoms, and one partially negative oxygen atom.

 Which of the following biological activities best demonstrates water’s adhesive properties?

• The vacuole of a plant cell swells as water enters and dilutes its contents.

• Water travels through vascular tissue from the roots to the leaves of a plant, moving against the force of gravity.

• A leaf’s cuticle, or waxy outer coating, repels water droplets.

• Water evaporates from leaves through openings called stomata, which open and close in response to environmental conditions.

The air temperature ranges of several Southern California cities in August are shown in the table below.

Which of the following best explains why coastal cities like San Diego often have a smaller air temperature range than inland cities?

• The adhesive properties of ocean water allow the water molecules to stick to one another, preventing temperature change of the air above it.

• Because water is less dense as a solid than as a liquid, it easily vaporizes, causing excess heat to escape into the air near coastal cities.

• The high heat capacity of water allows the ocean to moderate the temperature of nearby air and land.

• 
  The cohesive tendency of water molecules causes high surface tension, so heat is unable to penetrate the top layer of the ocean and escape into the air.

Which statement best describes why water is an effective solvent?

• Water is an ionic compound that attracts other like molecules.

• Water’s hydrophobic nature separates polar and non-polar substances.

• Water’s polarity allows it to dissolve ionic and polar compounds.
  Water’s relatively small size allows it to fit between individual atoms, driving them apart.

• 
  Water’s polarity allows it to dissolve ionic and polar compounds.

Bodies of water, such as ponds, freeze from top to bottom, forming a floating sheet of ice. This can help aquatic organisms survive during cold winter months.

Which of the following statements explains why the ice floats on the surface of the pond?

• As water freezes, ionic bonds form between water molecules, preventing the ice from sinking below the surface.

• The increased number of hydrogen bonds in ice compared to liquid water causes the water molecules in ice to be closer togethe

• The crystalline structure of solid ice makes it less dense than liquid water.

• The ice molecules have higher kinetic energy than the liquid water molecules, causing them to float.

Which of the following cations is likely to have the weakest attraction to an adjacent water molecule in an aqueous solution?

• Li+

• Ca2+

• Cs+

• Ba2+

Intramolecular hydrogen bonding occurs when a hydrogen bond forms between atoms in the same molecule. An example of this can be seen in salicylaldehyde, a compound commonly used to make perfumes. In molecules of salicylaldehyde, a hydrogen bond forms between two atoms that are nearby in space, resulting in a double-ring structure.

Which of the following diagrams correctly represents the intramolecular hydrogen bond (denoted by a dotted line) that forms in salicylaldehyde?

• 
• 
• 
• 

The Lewis structure of benzene is shown below.

Which of the following identifies all of the intermolecular forces present among molecules of benzene?

• London dispersion only

• Dipole-dipole

• london and dipole-dipole

• london and hydrogen bonding

The Lewis structure of methyl acetate is shown below.

Which of the following identifies all of the intermolecular forces present among molecules of methyl acetate?

• london

• dipole-dipole

• london and dipole

• london and hydrogen

The kinetic molecular theory relates macroscopic properties such as pressure, volume, and temperature to the microscopic motions of gas particles.

Consider the following statements:

A. There are no attractive or repulsive forces between the gas particles.

B. Gas particles are in constant, random motion only at temperatures above 0 degree

C. The volume of the individual gas particles must be taken into account when describing the volume of the gas itself.

Which statements are true according to the kinetic molecular theory?

• A only

• A and B

• A and C

• All of the above