102 ch 3
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?
1 × 10⁻¹⁰ mol of hydroxyl ion per liter of lake water
One liter of a solution of pH 2 has how many more hydrogen ions (H⁺) than 1 L of a solution of pH 6?
10,000 times more
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?
10.0°C
One liter of a solution of pH 9 has how many more hydroxyl ions (OH⁻) than 1 L of a solution of pH 4?
100,000 times more
How many molecules of glycerol (C₃H₈O₃; molecular mass = 92) would be present in 1 L of a 1 M glycerol solution?
6.02 × 10²³
Which of the following effects is produced by the high surface tension of water?
A water strider can walk across the surface of a small pond.
How would acidification of seawater affect marine organisms?
Acidification would decrease dissolved carbonate concentrations and hinder growth of corals and shell-building animals.
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 into the bloodstream. What will be the effect on pH of blood as that blood first comes in contact with respiring cells?
Blood pH will decrease slightly.
Why does ice float in liquid water
Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.
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.
Which of the following takes place as an ice cube cools a drink?
Kinetic energy in the drink decreases.
Which of the following ionizes completely in solution and is considered to be a strong
NaOH
Increased atmospheric CO₂ concentrations might have what effect on seawater?
Seawater will become more acidic, and carbonate concentrations will decrease.
Why does evaporation of water from a surface cause cooling of the surface?
The water molecules with the most heat energy evaporate more readily.
Which of the following statements is true about buffer solutions?
They maintain a relatively constant pH when either acids or bases are added to them.
One of the buffers that contribute to pH stability in human blood is carbonic acid (H₂CO₃). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO₃⁻ and a hydrogen ion (H⁺). Thus, H₂CO₃ ↔ HCO₃⁻ + H⁺ If the pH of the blood increases, one would expect
a decrease in the concentration of H₂CO₃ and an increase in the concentration of HCO₃⁻.
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 hydrogen bond
Liquid water's high specific heat is mainly a consequence of the
absorption and release of heat when hydrogen bonds break and form.
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 give H⁺ to weak acids, but accept H+ from strong acids
Buffers are substances that help resist shifts in pH by
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?
both increased acidity of the deep waters and changes in the growth of bottom-dwelling organisms with calcium carbonate shells
Water molecules are able to form hydrogen bonds with
compounds that have polar covalent bonds
f the pH of a solution is decreased from 9 to 8, it means that the
concentration of H⁺ has increased tenfold (10X) and the concentration of OH⁻ has decreased to one-tenth (1/10) what they were at pH 9.
If the pH of a solution is increased from pH 5 to pH 7, it means that the
concentration of OH⁻ is 100 times greater than what it was at pH 5.
Which type of bond must be broken for water to vaporize?
hydrogen bonds
The bonds that are broken when water vaporizes are
hydrogen bonds between water molecules.
A strong acid like HCl
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?
neutral
Hydrophobic substances such as vegetable oil are
nonpolar substances that repel water molecules
We can be sure that a mole of table sugar and a mole of vitamin C are equal in their
number of molecules.
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by
polar covalent bonds.
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, one would expect
the HCO₃⁻ to act as a base and remove excess H⁺ with the formation of H₂CO₃.
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?
the absorption of heat by the breaking of hydrogen bonds
If a solution has a pH of 7, this means that
the concentration of H⁺ ions in the water equals the concentration of OH⁻ ions in the water.
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.
the concentration of hydrogen ions in solution X is 1,000 times as great as the concentration of hydrogen ions in solution Y.
The partial negative charge in a molecule of water occurs because
the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus.
Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?
the release of heat by the formation of hydrogen bonds
Research indicates that acid precipitation can damage living organisms by
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?
wax
Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H₂S
will not form hydrogen bonds with each other.
