AP Bio Chapter 2

About 25 of the 92 natural elements are known to be essential to life. Which 4 of these 25 elements make up approximately 96% of living matter?

• carbon, sodium, hydrogen, nitrogen

• carbon, oxygen, phosphorus, hydrogen

• oxygen, hydrogen, calcium, nitrogen

• carbon, hydrogen, nitrogen, oxygen

• carbon, oxygen, nitrogen, calcium

Which of the following statements is false?

• Carbon, hydrogen, oxygen, and nitrogen are the most abundant elements of living matter.

• Some naturally occurring elements are toxic to organisms.

• All organisms require the same elements in the same quantities.

• Iron is an example of an element needed by all organisms.

• Approximately one-quarter of the natural elements are essential elements.

Why is each element unique and different from other elements with respect to its chemical properties?

• Each element has a unique atomic mass.

• Each element has a unique mass number.

• Each element has a unique number of protons.

• Each element has a unique number of neutrons.

• Each element has different radioactive properties.

The nucleus of a nitrogen atom contains 7 neutrons and 7 protons. Which of the following is a correct statement concerning nitrogen?

• The nitrogen atom has a mass number of approximately 7 and an atomic number of 14.

• The nitrogen atom has a mass number of approximately 14 and an atomic number of 7.

• The nitrogen atom has a mass number of approximately 14 and an atomic number of 14.

• The nitrogen atom has a mass number of approximately 7 and an atomic number of 21.

• The nitrogen atom has a mass number of approximately 14 and an atomic number of 21

Carbon-12 is the most common isotope of carbon and has a mass number of 12. However, the atomic mass of carbon is slightly more than 12 daltons. Why?

• The atomic mass does not include the mass of electrons.

• Some carbon atoms in nature have an extra proton.

• Some carbon atoms in nature have more neutrons.

• Some carbon atoms in nature have a different valence electron distribution.

• Some carbon atoms in nature have undergone radioactive decay.

An atom has 6 electrons in its outer shell. How many unpaired electrons does it have?

• 0

• 2

• 4

• 6

• 2 or 4

The atomic number of each atom is given to the left of each of the following elements. Which of the atoms has the same valence as carbon (12/6 C)

• 7N nitrogen

• 9F fluorine

• 10Ne neon

• 12Mg magnesium

• 14Si silicon

Which of the following molecules contains the most polar covalent bond?

• H2

• O2

• CO2

• H2O

• CH4

Which of the following correctly describes any reaction that has reached chemical equilibrium?

• The concentration of the reactants equals the concentration of the products.

• The rate of the forward reaction is equal to the rate of the reverse reaction.

• All of the reactants have been converted to the products of the reaction.

• All of the products have been converted to the reactants of the reaction.

• Both the forward and the reverse reactions have stopped with no net effect on the concentration of the reactants and the products.

Which of the following explains most specifically the attraction of water molecules to one another?

• nonpolar covalent bond

• polar covalent bond

• ionic bond

• hydrogen bond

• hydrophobic interaction

Which of the following takes place as an ice cube cools a drink?

• Molecular collisions in the drink increase.

• Kinetic energy in the drink decreases.

• A calorie of heat energy is transferred from the ice to the water of the drink.

• The specific heat of the water in the drink decreases.

• Evaporation of the water in the drink increases.

Liquid water's high specific heat is mainly a consequence of the

• small size of the water molecules.

• high specific heat of oxygen and hydrogen atoms.

• absorption and release of heat when hydrogen bonds break and form.

• fact that water is a poor heat conductor.

• higher density of liquid water than solid water (ice).

Which type of bond must be broken for water to vaporize?

• ionic bonds

• both hydrogen bonds and ionic bonds

• polar covalent bonds

• hydrogen bonds

• both polar covalent bonds and hydrogen bonds

Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?

• the change in density when it condenses to form a liquid or solid

• reactions with other atmospheric compounds

• the release of heat by the formation of hydrogen bonds

• the release of heat by the breaking of hydrogen bonds

• the high surface tension of water

Which of the following statements is true about buffer solutions?

• They maintain a constant pH when bases are added to them but not when acids are added to them.

• They maintain a constant pH when acids are added to them but not when bases are added to them.

• They maintain a relatively constant pH of approximately 7 when either acids or bases are added to them.

• They maintain a relatively constant pH when either acids or bases are added to them.

• They are found only in living systems and biological fluids.

Buffers are substances that help resist shifts in pH by

• releasing H+ to a solution when acids are added.

• donating H+ to a solution when bases are added.

• releasing OH- to a solution when bases are added.

• accepting H+ from a solution when acids are added.

• both donating H+ to a solution when bases are added and accepting H+ when acids are added.

One of the buffers that contributes to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). Thus,
H2CO3 ↔ HCO3- + H+
If the pH of the blood drops, one would expect

• a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3-.

• the concentration of hydroxide ion (OH-) to increase.

• the concentration of bicarbonate ion (HCO3-) to increase.

• the HCO3- to act as a base and remove excess H+ with the formation of H2CO3.

• the HCO3- to act as an acid and remove excess H+ with the formation of H2CO3.

Research indicates that acid precipitation can damage certain marine organisms by

• buffering ocean waters.

• decreasing the H+ concentration in oceans.

• increasing the OH- concentration in oceans.

• decreasing the concentration of carbonate ions in oceans.

• both decreasing the H+ concentration and increasing the OH- concentration in oceans.

Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that

• solution Y has no free hydrogen ions (H+).

• the concentration of hydrogen ions in solution X is 30 times as great as the concentration of hydrogen ions in solution Y.

• the concentration of hydrogen ions in solution Y is 1,000 times as great as the concentration of hydrogen ions in solution X.

• the concentration of hydrogen ions in solution X is 3 times as great as the concentration of hydrogen ions in solution Y.

• the concentration of hydrogen ions in solution X is 1,000 times as great as the concentration of hydrogen ions in solution Y.

Which of the following pairs of atoms would be most likely to form a polar covalent bond?

Which one of the following pairs of atoms would be most likely to form ions and thus an ionic bond?

Identical heat lamps are arranged to shine on identical containers of water and methanol (wood alcohol), so that each liquid absorbs the same amount of energy minute by minute. The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. Which of the following graphs correctly describes what will happen to the temperature of the water and the methanol?

A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?

• a compound with the same number of carbon atoms as the hormone

• a compound with the same molecular mass (measured in daltons) as the hormone

• a compound with the same three-dimensional shape as part of the hormone

• a compound with the same number of orbital electrons as the hormone

• a compound with the same number of hydrogen and nitrogen atoms as the hormone

The reactivity of an atom arises from

• the average distance of the outermost electron shell from the nucleus.

• the existence of unpaired electrons in the valence shell.

• the sum of the potential energies of all the electron shells.

• the potential energy of the valence shell.

• the energy difference between the s and p orbitals.

Which of the following is not considered to be a weak molecular interaction?

• a covalent bond

• a van der Waals interaction

• an ionic bond in the presence of water

• a hydrogen bond

• A and B only

Which one of the atoms shown would be most likely to form an anion with a charge of -1?