BIO 187 Chapter 3 - Study Guide.pdf

Study Guide: Chapter 3 - Water and the Fitness of the Environment 1) In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by what kinds of bonds? 2) The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called? 3) An example of a hydrogen bond is the bond between A) C and H in methane (CH4). B) the H of one water molecule and the O of another water molecule. C) Na+and Cl- in salt. D) the two hydrogen atoms in a molecule of hydrogen gas (H2). E) Mg+and Cl- in MgCl2. 4) Water is able to form hydrogen bonds because 5) What gives rise to the cohesiveness of water molecules? 6) Which of the following effects is produced by the high surface tension of water? A) Lakes don't freeze solid in winter, despite low temperatures. B) A water strider can walk across the surface of a small pond. C) Organisms resist temperature changes, although they give off heat due to chemical reactions. D) Water can act as a solvent. E) The pH of water remains exactly neutral. 7) What takes place as an ice cube cools a drink? 8) Define a kilocalorie. 9) The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20 kg of water how many degrees Celsius? 1 10) Water's high specific heat is mainly a consequence of what? 11) Which type of bond must be broken for water to vaporize? 12) You have two beakers; one contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen. 13) At what temperature is water at its densest? 14) Why does ice float in liquid water? The following question is based on Figure 3.1: solute molecule surrounded by a hydration shell of water. Figure 3.1 15) Based on your knowledge of the polarity of water molecules, the solute molecule most likely has what charge? 16) What does it mean to say that vegetable oil is hydrophobic? 2 17) Define the concept of a mole (mol) of a substance. 18) How many molecules of glucose (C6H2O6 molecular mass =180 daltons) would be present in one mole of glucose? 19) How many molecules of glycerol (C3H8O3) would be present in 1 L of a 1 M glycerol solution? 20) When an ionic compound such as sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of particles (molecules or ions)? A) 1 L of 0.5 M NaCl B) 1 L of 0.5 M glucose C) 1 L of 1.0 M NaCl D) 1 L of 1.0 M glucose E) C and D will contain equal numbers of particles. 21) The molecular mass of glucose is 180 g. Which of the following procedures should you carry out to make a 1 M solution of glucose? A) Dissolve 1 g of glucose in 1 L of water. B) Dissolve 180 g of glucose in 1 L of water. C) Dissolve 180 g of glucose in 100 g of water. D) Dissolve 180 mg (milligrams) of glucose in 1 L of water. E) Dissolve 180 g of glucose in water, and then add more water until the total volume of the solution is 1 L. 22) The molecular mass of glucose (C6H12O6) is 180 g. What procedure should you carry out to make a 0.5 M solution of glucose? 3 Figure 3.2 23) How many grams of the molecule in Figure 3.2 would be equal to 1 mol of the molecule? (Carbon = 12, Oxygen = 16, Hydrogen = 1) 24) How many grams of the molecule in Figure 3.2 would be required to make 1 L of a 0.5 M solution of the molecule? (Carbon = 12, Oxygen = 16, Hydrogen = 1) 25) How many grams of the molecule in Figure 3.2 would be required to make 2.5 L of a 1 M solution of the molecule? (Carbon = 12, Oxygen = 16, Hydrogen = 1) 26) Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O ? H2CO3. Carbonic acid (H2CO3) is a weak acid. Respiring cells release CO2. What prediction can we make about the pH of blood as that blood first comes in contact with respiring cells? 4 27) 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 non-polar, 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) B) C) D) E) 5 29) The molecular weight of water is 18 daltons. What is the molarity of 1 liter of pure water? 30) Pure, freshly-distilled water has a pH of 7. This means what relative to the concentration of H+ and OH- ions in the water? 31) Which of the following ionizes completely in solution and is considered to be a strong acid? A) NaOH B) HCl C) NH3 D) H2CO3 E) CH3COOH 32) Which of the following ionizes completely in solution and is considered to be a strong base (alkali)? A) NaCl B) HCl C) NH3 D) H2CO3 E) NaOH 34) A given solution contains 0.0001(10-4) moles of hydrogen ions [H+] per liter. Is this solution neutral, acidic, or basic, an H+ acceptor or an H+ donor? 35) A solution contains 0.0000001(10-7) moles of hydroxyl ions [OH-] per liter. Is this solution neutral, acidic, or basic, an H+ acceptor or an H+ donor? 36) What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M? 6 37) What is the pH of a solution with a hydrogen ion [H+] concentration of 10-8 M? 38) Which of the following solutions has the greatest concentration of hydrogen ions [H+]? A) gastric juice at pH 2 B) vinegar at pH 3 C) tomato juice at pH 4 D) black coffee at pH 5 E) household bleach at pH 12 39) Which of the following solutions has the greatest concentration of hydroxyl ions [OH-]? A) lemon juice at pH 2 B) vinegar at pH 3 C) tomato juice at pH 4 D) urine at pH 6 E) seawater at pH 8 40) If the pH of a solution is decreased from 9 to 8 how has the concentration of H+ and OH- changed? A) concentration of H+ has decreased to one-tenth (1/10) what it was at pH 9. B) concentration of H+ has increased 10-fold (10X) compared to what it was at pH 9. C) concentration of OH- has increased 10-fold (10X) compared to what it was at pH 9. D) concentration of OH- has decreased to one-tenth (1/10) what it was at pH 9. E) Both B and D are correct. 41) If the pH of a solution is increased from pH 5 to pH 7 how has the concentration of OH- changed? 42) One liter of a solution of pH 2 has how many more hydrogen ions (H+) than 1 L of a solution of pH 6? A) 4 times more B) 400 times more C) 4,000 times more D) 10,000 times more E) 100,000 times more 43) One liter of a solution pH 9 has how many more hydroxyl ions (OH-) than 1 L of a solution of pH 4? 7 44) 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. 45) 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. 46) One of the buffers that contribute 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, how would this buffer function to buffer blood pH? A) a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3-. B) the concentration of hydroxide ion (OH-) to increase. C) the concentration of bicarbonate ion (HCO3-) to increase. D) the HCO3- to act as a base and remove excess H+ with the formation of H2CO3. E) the HCO3- to act as an acid and remove excess H+ with the formation of H2CO3. 47) Assume that acid rain has lowered the pH of a particular lake to pH 4.0. What is the hydroxyl ion concentration of this lake? 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 8 48) Research indicates that acid precipitation can damage living organisms by? 49) Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O ? H2CO3. Carbonic acid (H2CO3) is a weak acid. If CO2 is bubbled into a beaker containing pure, freshly-distilled water, which of the following graphs correctly describes the results? A) B) C) D) E) 9 Self-Quiz Questions 1) 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) water's change in density when it condenses B) water's 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) water's high surface tension 2) A slice of pizza has 500 kcal. If we could burn the pizza and use all the heat to warm a 50-L container of cold water, what would be the approximate increase in the temperature of the water? (Note: A liter of cold water weighs about 1 kg.) A) 50°C B) 5°C C) 10°C D) 100°C E) 1°C 3) The bonds that are broken when water vaporizes are A) ionic bonds. B) hydrogen bonds between water molecules. C) covalent bonds between atoms within water molecules. D) polar covalent bonds. E) nonpolar covalent bonds 4) Which of the following is a hydrophobic material? A) paper B) table salt 10 C) wax D) sugar E) pasta 5) We can be sure that a mole of table sugar and a mole of vitamin C are equal in their A) mass in daltons. B) mass in grams. C) number of molecules. D) number of atoms. E) volume. 6) How many grams of acetic acid (C2H4O2) would you use to make 10 L of a 0.1 M aqueous solution of acetic acid? (Note: The atomic masses, in daltons, are approximately 12 for carbon, 1 for hydrogen, and 16 for oxygen.) A) 10.0 g B) 0.1 g C) 6.0 g D) 60.0 g E) 0.6 g 7) Measurements show that the pH of a particular lake is 4.0. What is the hydrogen ion concentration of the lake? A) 4.0 M B) 10-10 M C) 10-4 M D) 104 M E) 4% 8) What is the hydroxide ion concentration of the lake described in question 7? A) 10-7 M B) 10-4 M C) 10-10 M D) 10-14 M E) 10 M 9) Draw three water molecules and label the atoms. Draw solid lines to indicate covalent bonds and dotted lines for hydrogen bonds. Add partial charge labels as appropriate. Answer: 11 12 Enter Your Information Biology, 8e (Campbell)