Module 2; Water and Life

How many molecules of glucose (C6H12O6 molecular mass = 180 daltons) would be present in 90 grams of glucose? 90 x 1023 (6.02/180) x 1023 (6.02/90) x 1023 (90 x 6.02) x 1023 (90/180) x 6.02 x 1023

(90/180) x 6.02 x 1023

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 solute particles (molecules or ions)? 1 L of 0.5 M NaCl 1 L of 0.5 M glucose 1 L of 1.0 M NaCl 1 L of 1.0 M glucose 1 L of 1.0 M NaCl and 1 L of 1.0 M glucose will contain equal numbers of solute particles

1 L of 1.0 M NaCl

What is the hydrogen ion [H+] concentration of a solution of pH 8? 8 M 8 x 10-6 M 0.01 M 10-8 M 10-6 M

10-8 M

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.) 50°C 5°C 1°C 100°C 10°C

10°C

How many grams of the compound in the figure above would be required to make 1 L of a 0.5 M solution? (carbon = 12, oxygen = 16, hydrogen = 1) 29 30 60 150 342

30

The molecular weight of water is 18 daltons. What is the molarity of 1 liter of pure water? (Hint: What is the mass of 1 liter of pure water?) 55.6 M 18 M 37 M 0.66 M 1.0 M

55.6 M

You have a freshly prepared 1 M solution of glucose in water. You carefully pour out a 100 mL sample of that solution. How many glucose molecules are included in that 100 mL sample? 6.02 x 1023 3.01 x 1023 6.02 x 1024 12.04 x 1023 6.02 x 1022

6.02 x 1022

How many grams would be equal to 1 mol of the compound shown in the figure above? (carbon = 12, oxygen = 16, hydrogen = 1) 29 30 60 150 342

60

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.) 10 g 0.1 g 6.0 g 60 g 0.6 g

60 g

A 0.01 M solution of a substance has a pH of 2. What can you conclude about this substance? It is a strong acid that ionizes completely in water. It is a strong base that ionizes completely in water. It is a weak acid. It is a weak base. It is neither an acid nor a base.

It is a strong acid that ionizes completely in water.

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.

Kinetic energy in the drink decreases.

A beaker contains 100 mL of NaOH solution at pH = 13. A technician carefully pours into the beaker 10 mL of HCl at pH = 1. Which of the following statements correctly describes the results of this mixing? The concentration of Na+ ion rises. The concentration of Cl- ion will be 0.1 M. The concentration of undissociated H2O molecules remains unchanged. The pH of the beaker's contents will be neutral. The pH of the beaker's contents falls.

The pH of the beaker's contents falls.

Why does evaporation of water from a surface cause cooling of the surface? The breaking of bonds between water molecules absorbs heat. The water molecules with the most heat energy evaporate more readily. The solute molecules left behind absorb heat. Water molecules absorb heat from the surface in order to acquire enough energy to evaporate. The expansion of water vapor extracts heat from the surface.

The water molecules with the most heat energy evaporate more readily.

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? a covalent bond a hydrogen bond an ionic bond a hydrophilic bond a van der Waals interaction

a hydrogen bond

A given solution contains 0.0001(10-4) moles of hydrogen ions [H+] per liter. Which of the following best describes this solution? acidic: will accept H+ from both strong and weak acids basic: will accept H+ from both strong and weak acids acidic: will give H+ to weak acids, but accept H+ from strong acids basic: will give H+ to weak acids, but accept H+ from weak acids acidic: will give H+ to both strong and weak acids

acidic: will give H+ to weak acids, but accept H+ from strong acids

One mole (mol) of glucose (molecular mass = 180 daltons) is 180 x 1023 molecules of glucose. 1 kg of glucose dissolved in 1 L of solution. the largest amount of glucose that can be dissolved in 1 L of solution. 180 kilograms of glucose. both 180 grams of glucose and 6.02 x 1023 molecules of glucose.

both 180 grams of glucose and 6.02 x 1023 molecules of glucose.

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.

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

One idea to mitigate the effects of burning fossil fuels on atmospheric CO2 concentrations is to pipe liquid CO2 into the ocean at depths of 2,500 feet or greater. At the high pressures at such depths, CO2 is heavier than water. What potential effects might result from implementing such a scheme? increased photosynthetic carbon fixation because of the increased dissolved carbon dioxide in the deep water increased carbonate concentrations in the deep waters reduced growth of corals from a change in the carbonate-bicarbonate equilibrium no effect because carbon dioxide is not soluble in water both increased acidity of the deep waters and changes in the growth of bottom-dwelling organisms with calcium carbonate shells

both increased acidity of the deep waters and changes in the growth of bottom-dwelling organisms with calcium carbonate shells

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?

graph with a slowly decreasing line

The bonds that are broken when water vaporizes are ionic bonds. hydrogen bonds between water molecules. covalent bonds between atoms within water molecules. polar covalent bonds. nonpolar covalent bonds.

hydrogen bonds between water molecules.

A strong acid like HCl ionizes completely in an aqueous solution. increases the pH when added to an aqueous solution. reacts with strong bases to create a buffered solution. is a strong buffer at low pH. both ionizes completely in aqueous solutions and is a strong buffer at low pH

ionizes completely in an aqueous solution.

A solution contains 0.0000001(10-7) moles of hydroxyl ions [OH-] per liter. Which of the following best describes this solution? acidic: H+ acceptor basic: H+ acceptor acidic: H+ donor basic: H+ donor neutral

neutral

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

nonpolar substances that repel water molecules.

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

polar covalent bonds.

Based on your knowledge of the polarity of water molecules, the solute molecule depicted here is most likely positively charged. negatively charged. without charge. hydrophobic. nonpolar.

positively charged.

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? water's change in density when it condenses water's ability to dissolve molecules in the air the release of heat by the formation of hydrogen bonds the absorption of heat by the breaking of hydrogen bonds water's high surface tension

the absorption of heat by the breaking of hydrogen bonds

If the cytoplasm of a cell is at pH 7, and the mitochondrial matrix is at pH 8, this means that the concentration of H+ ions is tenfold higher in the cytoplasm than in the mitochondrial matrix. the concentration of H+ ions is tenfold higher in the mitochondrial matrix than in the cytoplasm. the concentration of H+ ions in the cytoplasm is 7/8 the concentration in the mitochondrial matrix. the mitochondrial matrix is more acidic than the cytoplasm. the concentration of H+ ions in the cytoplasm is 8/7 the concentration in the mitochondrial matrix.

the concentration of H+ ions is tenfold higher in the cytoplasm than in the mitochondrial matrix.

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.

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

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

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

Which of the following is a hydrophobic material? paper table salt wax sugar pasta

wax