Chapter 3 BIO

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by A) hydrogen bonds. B) nonpolar covalent bonds. C) polar covalent bonds. D) ionic bonds. E) van der Waals interactions.

C) polar covalent bonds.

Hydrophobic substances such as vegetable oil are B) nonpolar substances that have an attraction for water molecules. C) polar substances that repel water molecules. D) polar substances that have an affinity for water. E) charged molecules that hydrogen-bond with water molecules.

A) nonpolar substances that repel water molecules.

Which of the following ionizes completely in solution and is considered to be a strong acid? A) NaOH C) NH3 D) H2CO3 E) CH3COOH

B) HCl

Waterʹs high specific heat is mainly a consequence of the A) small size of the water molecules. B) high specific heat of oxygen and hydrogen atoms. D) fact that water is a poor heat conductor. E) inability of water to dissipate heat into dry air.

C) absorption and release of heat when hydrogen bonds break and form.

Water is able to form hydrogen bonds because A) oxygen has a valence of 2. B) the water molecule is shaped like a tetrahedron. D) the oxygen atom in a water molecule has a weak positive charge. E) each of the hydrogen atoms in a water molecule is weakly negative in charge.

C) the bonds that hold together the atoms in a water molecule are polar covalent bonds.

Pure, freshly-distilled water has a pH of 7. This means that A) there are no H+ ions in the water. B) there are no OH- ions in the water. C) the concentration of H+ ions in the water equals the concentration of OH- ions in the water. D) the concentration of H+ ions in the water is 7 times the concentration of OH- ions in the water. E) The concentration of OH- ions in the water is 7 times the concentration of H+ ions in the water.

C) the concentration of H+ ions in the water equals the concentration of OH- ions in the water.

Why does ice float in liquid water? A) The liquid water molecules have more kinetic energy and thus support the ice. B) The ionic bonds between the molecules in ice prevent the ice from sinking. C) Ice always has air bubbles that keep it afloat. D) Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water. E) The crystalline lattice of ice causes it to be denser than liquid water.

D) Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.

Which of the following statements is true about buffer solutions? A) They maintain a constant pH when bases are added to them but not when acids are added to them. B) They maintain a constant pH when acids are added to them but not when bases are added to them. C) They maintain a constant pH of exactly 7 in all living cells and biological fluids. D) They maintain a relatively constant pH when either acids or bases are added to them. E) They are found only in living systems and biological fluids.

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

What gives rise to the cohesiveness of water molecules? A) hydrophobic interactions B) nonpolar covalent bonds C) ionic bonds E) both A and C

D) hydrogen bonds

Which type of bond must be broken for water to vaporize? A) ionic bonds B) nonpolar covalent bonds C) polar covalent bonds E) covalent bonds

D) hydrogen bonds

Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature? A) waterʹs change in density when it condenses B) waterʹs ability to dissolve molecules in the air C) the release of heat by the formation of hydrogen bonds D) the absorption of heat by the breaking of hydrogen bonds E) waterʹs high surface tension

D) the absorption of heat by the breaking of hydrogen bonds

Research indicates that acid precipitation can damage living organisms by A) buffering aquatic systems such as lakes and streams. B) decreasing the H+ concentration of lakes and streams. C) increasing the OH- concentration of lakes and streams. D) washing away certain mineral ions that help buffer soil solution and are essential nutrients for plant growth. E) both B and C

D) washing away certain mineral ions that help buffer soil solution and are essential nutrients for plant growth.

A strong acid like HCL_______

Dissociates completely in an aqueous solution

Buffers are substances that help resist shifts in pH by A) releasing H+ in acidic solutions. B) donating H+ to a solution when they have been depleted. C) releasing OH- in basic solutions. D) accepting H+ when the are in excess. E) Both B and D are correct.

E) Both B and D are correct.