Biology: Ch. 3-4 Water & Carbon: Exam 1 Review

Which of these groups is characteristic of thiols?

-SH. Thiols are characterized by the presence of a sulfhydryl group

About _____ molecules in a glass of water are dissociated.

1 in 500,000,000

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

What is the charge on a hydronium ion?

1+

A pH of 6 is how many times more acidic than a pH of 9?

1,000

What is the charge on a hydroxide ion?

1-

What is the hydroxyl ion (OH-) concentration of a solution of pH 8?

10-6 M

What is the hydrogen ion [H+H+] concentration of a solution of pH 8?

10-8 M

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

A solution with a pH of 2 has how many more protons in it than a solution with a pH of 4?

100 times more

What is the pH of an aqueous solution with the hydronium ion concentration[H3O+] = 2 x 10-14 M ?

13.7

How many grams of the compound in the figure above would be required to make 2.5 L of a 1 M solution?(carbon = 12, oxygen = 16, hydrogen = 1)

150

How many structural isomers are possible for a substance having the molecular formula C4H10C4H10?

2

The molecular weight of water is 18 daltons. What is the molarity of 1 liter of pure water? (Hint: Note that 1 liter of pure water has a mass of 1 kg.)

55.6 M

You have a freshly prepared 0.1 M solution of glucose in water. Each liter of this solution contains how many glucose molecules?

6.02 × 1022

Carbonated cola is more acidic than coffee or even orange juice because cola contains phosphoric acid. What is the molar concentration of [H3O+] in a cola that has a pH of 3.120?

7.59 × 10−4. The molar concentration of [H3O+] in a cola with a pH of 3.120 can be calculated this way: [H3O+]=10−pH[H3O+]=10−pH [H3O+]=10−3.120[H3O+]=10−3.120 [H3O+]=7.59×10−4M[H3O+]=7.59×10−4M Ingestion of large amounts of phosphoric acid found in cola can upset the body's regulation of bone metabolism and reduce the absorption of calcium from the diet. For this reason, people who are at risk of developing osteoporosis are often advised not to drink much cola.

Select the statement that best describes a buffer.

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.

The molecule shown here contains four functional groups. Highlight all the atoms of the four functional groups, but do not highlight any bonds.

A functional group is a group of atoms bonded together in a specific way that can replace a hydrogen atom in a hydrocarbon. The molecule shown here contains four functional groups (−OH−OH, −SH−SH, −NH2−NH2, and −OPO2−3−OPO32−) attached to a carbon chain that is six carbon atoms long.

Which statement about a methyl functional group is correct?

A methyl group consists of a carbon bonded to three hydrogen atoms.A methyl group consists of a carbon covalently bonded to three hydrogen atoms.

How did this molecule form?

A water molecule gained an hydrogen ion from another water molecule.

Identify the functional groups.

Amino and carboxyl are functional groups. Read about the variety of biologically important functional groups and note the structure and functional properties of amino and carboxyl groups.

Carbon dioxide (CO2CO2) is readily soluble in water, according to the equation CO2CO2 + H2OH2O ↔↔ H2CO3H2CO3. Carbonic acid (H2CO3H2CO3) is a weak acid. Respiring cells release CO2CO2 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.

Which of functional groups listed below behaves as an acid?

By donating hydrogen ions, carboxyl groups act as an acid.

Which of the following is a hydrocarbon?

C3H8 This is a typical hydrocarbon with single covalent bonds; the number of hydrogen atoms is equal to two times the number of carbon atoms plus 2.

The molar mass of glucose (C6H12O6C6H12O6) is 180 g/mol. Which of the following procedures should you carry out to make a 0.5 M solution of glucose?

Dissolve 90 g of glucose in a small volume of water, and then add more water until the total volume of the solution is 1 L.

Which statement about isomers is correct?

Enantiomers differ in biological activity.

Which of these is the correct equation for the dissociation of water?

H2O + H2O <==> H3O+ + OH-

Most organic compounds contain carbon and _____.

Hydrogen

Which of these functional groups is characteristic of alcohol?

Hydroxyl groups are characteristic of alcohol.

How do isomers differ from one another?

Isomers differ in the arrangement or bonding of atoms.

L-dopa is used to treat _____.

Parkinson's disease

Which of these groups plays a major role in energy transfer?

Phosphate groups are a component of ATP.

Increased atmospheric CO2 concentrations might have what effect on seawater?

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

Rank the following from most acidic to least acidic.

The 10-6 M H3O+ solution has a pH of 6, and the 10-2 M H3O+ solution has a pH of 2. The solutions are ranked from most acidic (pH = 2) to most basic (pH = 14).

Look at the figure showing the pH values of some familiar aqueous solutions. What is the difference between H+ concentration in an acidic solution such as lemon juice (pH 2) and a basic solution such as household bleach (pH 13)?

The H+ concentration of lemon juice is higher than the H+ concentration of household bleach by a factor of 1011 (100 billion). The figure shows the pH scale and pH values of some aqueous solutions, including lemon juice and household bleach. The pH of a solution is the negative logarithm of H+ concentration.

Which of the functional groups shown above is most likely to gain a proton and become positively charged?

The amino group is most likely to gain a proton. An amino group acts as a base and can pick up protons from the surrounding medium, becoming positively charged

Which of the functional groups behaves as a base?

The electronegativity of nitrogen means that amino groups tend to pick up hydrogen ions.

Which one of these is an amino group?

This is an amino group, NH2.

Identify all correct statements about the ionization of water.

Water ionizes to form hydroxide and hydronium ions. Dissociation of water is reversible. Dissociation of water produces equal numbers of OH- and H+.

A given solution contains 0.0001(10-4) moles of hydrogen ions [H+H+] per liter. Which of the following best describes this solution?

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

Which property of water allows a paper towel to pick up a puddle of water?

adhesion of water molecules to other kinds of molecules

Organic molecules with only hydrogens and five carbon atoms can have different structures in all of the following ways except

by forming enantiomers.

The large diversity of shapes of biological molecules is possible because of the extensive presence of _____ in the molecules.

carbon

Citric acid makes lemons taste sour. Which of the following is a functional group that would cause a molecule such as citric acid to be acidic?

carboxyl, The carboxyl group can release a hydrogen ion when in solution.

Cis-trans isomers (geometric isomers) are molecules that _____.

differ in the arrangement of their atoms about a double bond

In a neutral solution the concentration of _____.

hydrogen ions is equal to the concentration of hydroxide ions

What name is given to this molecule?

hydronium ion

What name is given to this molecule?

hydroxide ion

An acid is a substance that _____.

increases the hydrogen ion concentration of an aqueous solution

Molecules that have the same chemical formula (same numbers of each atom) but different three-dimensional shapes are called _____.

isomers

What kind of effect does R-dopa have on Parkinson's disease?

none

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

pH 4

What functional group is commonly used in cells to transfer energy from one organic molecule to another?

phosphate, The addition and release of phosphate groups to and from ADP and ATP is how cells store chemical energy and expend it to accomplish work.

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 1000 times as great as the concentration of hydrogen ions in solution Y

Variations in the reactive properties of different organic molecules are most closely associated with _____.

the presence or absence of functional groups, Functional groups are the most common participants in chemical reactions.

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

Which property of water allows dogs to cool themselves by panting?

water's high heat of vaporization

Which property of water allows a water strider to walk on water?

water's high surface tension, Water's high surface tension, related to its cohesion, makes water behave as though coated with an invisible film.

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.