mastering bio ch 3: polarity of water

A pH of 6 is how many times more acidic than a pH of 9? -3 -30 -100 -300 -1,000

1,000

what is the pH scale out of?

14

Select the statement that best describes a buffer. -A buffer prevents the pH of a solution from changing when an acid or base is added. -A buffer causes acidic solutions to become alkaline, and alkaline solutions to become acidic. -A buffer stabilizes the pH of a solution by preventing acids or bases from dissociating. -A buffer resists change in pH by accepting hydrogen ions when acids are added to the solution and donating hydrogen ions when bases are added. -Buffered solutions are always neutral, with a pH of 7.

A buffer resists change in pH by accepting hydrogen ions when acids are added to the solution and donating hydrogen ions when bases are added.

Increased atmospheric CO2 concentrations might have what effect on seawater? -Seawater will become more alkaline, and carbonate concentrations will decrease. -Seawater will become more acidic, and carbonate concentrations will decrease. -There will be no change in the pH of seawater, because carbonate will turn to bicarbonate. -Seawater will become more acidic, and carbonate concentrations will increase

Seawater will become more acidic, and carbonate concentrations will decrease.

What is the pH of a solution with a hydroxyl ion (OH-) concentration of 10-12 M?

pH 2

The unequal sharing of electrons within a water molecule makes the water molecule _____. -change easily from a liquid to gaseous form -have a low surface tension -polar -ionic -hydrophobic

polar

The water molecules in the diagram are attracted to the cell walls of water-conducting cells by adhesion due to hydrogen bonds. What conclusion is supported by this information? -Cell walls of plants are formed from the products of photosynthesis. -Cell walls of plants contain molecular grooves that physically hold the water molecule. -Cell walls of plants contain oxygen and/or nitrogen and are therefore polar. -Cell walls of plants are composed of non-polar molecules.

Cell walls of plants contain oxygen and/or nitrogen and are therefore polar.

what is considered the weakest bond?

Hydrogen bonds because they do not involve the sharing of electrons

Which of the following takes place as an ice cube cools a drink? -Molecular collisions in the drink increase. -The specific heat of the water in the drink decreases. -Kinetic energy in the liquid water decreases. -A calorie of heat energy is transferred from the ice to the water of the drink.

Kinetic energy in the liquid water decreases

In living systems molecules involved in hydrogen bonding almost always contain either oxygen or nitrogen or both. How do you explain this phenomenon? -Oxygen and nitrogen were both components of gases that made up the early atmosphere on Earth. -Oxygen and nitrogen are elements found in both nucleic acids and proteins. -Oxygen and nitrogen are elements found in fats and carbohydrates. -Oxygen and nitrogen are elements with very high attractions for their electrons.

Oxygen and nitrogen are elements with very high attractions for their electrons.

The loss of water from a plant by transpiration cools the leaf. Movement of water in transpiration requires both adhesion to the conducting walls and wood fibers of the plant and cohesion of the molecules to each other. A scientist wanted to increase the rate of transpiration of a crop species to extend its range into warmer climates. The scientist substituted a nonpolar solution with an atomic mass similar to that of water for hydrating the plants. What do you expect the scientists data will indicate from this experiment?

Transpiration rates will fall to zero as nonpolar compounds do not have the properties necessary for adhesion and cohesion.

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+), as noted below. H2CO3 <-> HCO3- + H+ If the pH of blood increases, one would expect _____. -a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3- -a decrease in the concentration of HCO3- and an increase in the concentration of H+ -an increase in the concentration of HCO3- and a decrease in the concentration of OH- -an increase in the concentration of H2CO3 and a decrease in the concentration of HCO3-

a decrease in the concentration of H2CO3 and an increase in the concentration of H+

Water molecules can form hydrogen bonds with _____. -oils -compounds that have polar covalent bonds -chloride ions -oxygen gas (O2) molecules

compounds that have polar covalent bonds

A strong acid like HCl _____. -increases the pH when added to an aqueous solution -is a strong buffer at low pH -reacts with strong bases to create a buffered solution -dissociates completely in an aqueous solution

dissociates completely in an aqueous solution

The tendency of an atom to pull electrons toward itself is referred to as its _____. -covalency -tonicity -electronegativity -polarity -ionic potential

electronegativity

What process exerts the pull on water molecules that is relayed from leaf to root via cohesion? -gravity -evaporation -precipitation -antigravity

evaporation

A water molecule can bond to up to _____ other water molecules by ____ bonds. -four ... hydrogen -two ... polar covalent -three ... ionic -four ... polar covalent -two ... hydrogen

four ... hydrogen

Which of the following is a property of liquid water? Liquid water _____. -has a heat of vaporization that is higher than that for most other substances -is nonpolar -is less dense than ice -has a specific heat that is lower than that for most other substances

has a heat of vaporization that is higher than that for most other substances

Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's _____.

high specific heat

the _______________of water allows the insect to remain on the surface.

high surface tension

The partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called? -an ionic bond -a hydrogen bond -a covalent bond -a van der Waals interaction

hydrogen bond

An acid is a substance that _____. -is a versatile solvent -forms covalent bonds with other substances -reduces the hydrogen ion concentration of a solution -contains hydrogen -increases the hydrogen ion concentration of an aqueous solution

increases the hydrogen ion concentration of an aqueous solution

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

nonpolar substances that repel water molecules