Chapter 3 Review

C REASON: nonpolar and nonionic

D REASON: 1 mole of a substance has the same # of molecules as 1 mole of another substance

(C) REASON: pH of the lake is 4... use the formula 10^-pH to find the hydrogen ion concentration, which is 10^-4

(A) REASON: [H+][OH-] = 10^-14

D REASON: 500 (kg * degrees C) divided by 50 kg (since 1L cold water = 1 kg)

A REASON: absorption of heat by breaking bonds cools down surroundings => sweating

B REASON: water's high heat of vaporization results in evaporative cooling => surface of water cools down this occurs b/c "hottest" (fast) molecules have already escaped into vapor, making the remaining molecules cool

C REASON: definition of a polar molecule (uneven sharing of electrons; more electronegative leads to strongly pulling more shared electrons towards itself)

E REASON: water moves up a plant because of h-bonds due to cohesion (between H2O molecules in cell walls) AND adhesion (between H2O molecules and cell walls to go against gravity)

C REASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.

D REASON: Good! When sugar dissolves in water, the sugar molecules remain intact but mingle with water molecules. When salt (NaCl) dissolves, its Na+ and Cl- ions separately mingle with water.

D REASON: Good answer! Many reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.

E REASON: Good choice! The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.

A REASON: Good job! When you heat water, much of the heat is used to break hydrogen bonds. Only the remaining heat can increase molecular motion, raising the temperature.

D REASON: Good choice! Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.

C REASON: Correct! At boiling, all the added heat is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature.

E REASON: Correct! The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.

C REASON: Correct! Water molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.

E REASON: Polar attractions occur between atoms with partial charges and are weaker than covalent bonds. Still, they're important because so many of them occur in living cells.

B REASON: They can also form between H and other highly electronegative atoms, such as O, if the atoms have strong partial charges.

B REASON: it makes H3O+ and OH-, not H+ and OH-

C

D REASON: Hydrophobic substances do not have an affinity for water. Substances that are nonionic and nonpolar (or otherwise cannot form hydrogen bonds) actually seem to repel water; these substances are said to be hydrophobic.

A REASON: Oxygen is one of the most electronegative of all the elements, attracting shared electrons much more strongly than hydrogen does. In a covalent bond between oxygen and hydrogen, the electrons spend more time near the oxygen nucleus than they do near the hydrogen nucleus. Because electrons have a negative charge and are pulled toward oxygen in a water molecule, the oxygen atom has a partial negative charge.

A REASON: Surface tension, adhesion, partial changes on the oxygen and hydrogen, and cohesion are hydrogen bonding properties, but nonpolar covalent bonding is not. Water's polar nature is responsible for these properties. The extraordinary qualities of water are emergent properties resulting from hydrogen bonding.

D REASON: The absorption of human-generated CO2 by the oceans increases the oceanic concentration of carbonic acid because it reacts with water to form carbonic acid, it increases the oceans' acidity and lowers the pH of seawater, reduces the carbonate ion concentration in the oceans and threatens calcifying organisms in marine ecosystems because the absorption of CO2 by the oceans leads to a decrease in the carbonate ion concentration, which is required for calcification, the production of calcium carbonate (CaCO3) by many marine organisms, and increases the hydrogen ion concentration in the oceans but decreases the carbonate ion concentration and threatens the livability of the oceans for calcifying organisms.