Unit 1 Water, Thermoregulation, Plant Transport

Hydrophobic substances such as hydrocarbons or vegetable oil are Selected: a. nonpolar substances that repel water molecules.This answer is correct. 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

The following question is based on Figure 3.1: solute molecule surrounded by a hydration shell of water. Based on your knowledge of the polarity of water molecules, the solute molecule is most likely Selected: a. positively charged.This answer is correct. b. negatively charged. c. without charge. d. hydrophobic. e. nonpolar.

a

Identical heat lamps are arranged to shine on identical containers of water and methanol (alcohol), so that each liquid absorbs the same amount of energy minute by minute. The covalent bonds of methanol molecules are mostly non-polar, so there are few hydrogen bonds among methanol molecules. Which of the following graphs correctly describes what will happen to the temperature of the water and the methanol?

b

Water's 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. Selected: c. absorption and release of heat when hydrogen bonds break and form.This answer is correct. d. fact that water is a poor heat conductor. e. inability of water to dissipate heat into dry air.

c

water is able to form hydrogen bonds because: a) oxygen has a valence of 2 b) the water molecule is shaped like a tetrahedron c) the bonds that hold together the atoms in a water molecule are polar covalent d) the oxygen atom in a water molecule has weak positive charge e) each of the hydrogen atoms in a water molecule is weakly negative in charge

c

One of the buffers that contribute to pH stability in human blood is carbonic acid (mc007-1.jpg). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (mc007-2.jpg) and a hydrogen ion (Hmc007-3.jpg). Thus, mc007-4.jpg If the pH of the blood drops, one would expect a. a decrease in the concentration of mc007-5.jpg and an increase in the concentration of mc007-6.jpg. b. the concentration of hydroxide ion (OHmc007-7.jpg) to increase. c. the concentration of bicarbonate ion (mc007-8.jpg) to increase. Selected: d. the mc007-9.jpg to act as a base and remove excess H+ with the formation of mc007-10.jpg.This answer is correct. e. the mc007-11.jpg to act as an acid and remove excess H+ with the formation of mc007-12.jpg.

d

Buffers are substances that help resist shifts in pH by a. releasing Hmc006-1.jpg in acidic solutions. b. donating Hmc006-2.jpg to a solution when they have been depleted. c. releasing OHmc006-3.jpg in basic solutions. Selected: d. accepting Hmc006-4.jpg when the are in excess.This answer is incorrect. e. Both B and D are correct.

e