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A covalent bond is one in which
outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms
what results from an unseal sharing of electrons between atoms
a polar covalent bond
The nuclear of a nitrogen atom contains 7 neutrons and 7 protons. Which of the following is a correct statement concerning nitrogen?
The nitrogen atom has a mass number of 14 and an atomic mass of approximately 14 daltons.
A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?
a compound with the same three–dimensional shape as part of the hormone
Carbon–12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. A mole of carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why?
Some carbon atoms in nature have more neutrons.
If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the most problems for this animal?
a surface made with carbon and hydrogen atoms covalently bonded together
One difference between carbon
is that carbon
has
two more neutrons than carbon–12.
Compared with 31P, the radioactive isotope 32P has
one more neutron.
Which of the following explains most specifically the attraction of water molecules to one another?
hydrogen bond
Atoms whose outer electron shells contain 8 electrons tend to
be both chemically inert and gaseous at room temperature.
In the term trace element, the modifier trace means that
the element is required in very small amounts.
Knowing just the atomic mass of an element allows inferences about which of the following?
the number of protons plus neutrons in the element
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?
carbon, hydrogen, nitrogen, oxygen
When two atoms are equally electronegative, they will interact to form
nonpolar covalent bonds.
Which of the following correctly describes any reaction that has reached chemical equilibrium?
The rate of the forward reaction is equal to the rate of the reverse reaction.
Which of these systems is least likely to be at chemical equilibrium?
a test tube of living cells
Which of the following is not considered to be a weak molecular interaction?
a covalent bond
What coefficients must be placed in the following blanks so that all atoms are accounted for in the products?
C6H12O6 → _____ C2H6O + _____ CO2
2; 2
If an atom of sulfur (atomic number 16) were allowed to react with atoms of hydrogen (atomic number 1), which of the molecules below would be formed?
H—S—H
Carbon dioxide (CO2) is readily soluble in water, according to the equation CO 2 + H2O ↔ H2CO3. Carbonic acid (H2CO3) is a weak acid. If CO2is bubbled into a beaker containing pure, freshly distilled water, which of the following graphs correctly describes the results?
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.
Which type of bond must be broken for water to vaporize?
hydrogen bonds
What is the hydrogen ion [H+] concentration of a solution of pH 8?
10–8 M
Which of the following is a hydrophobic material?
wax
Liquid water's high specific heat is mainly a consequence of the
absorption and release of heat when hydrogen bonds break and form.
absorption and release of heat when hydrogen bonds break and form. - no response given
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.
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by
polar covalent bonds.
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
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 1.0 M NaCl
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.
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.
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.
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.
Why does evaporation of water from a surface cause cooling of the surface?
The water molecules with the most heat energy evaporate more readily.
Measurements show that the pH of a particular lake is 4.0. What is the hydroxide ion concentration of the lake?
10–10 M
Which of these molecules would be soluble in water?
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
Increased atmospheric CO2 concentrations might have what effect on seawater?
Seawater will become more acidic, and carbonate concentrations will decrease.
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.
The two molecules shown in the figure above are best described as
structural isomers.
The two molecules shown in the figure above are best described as
cis–trans isomers.
Which molecule shown above can increase the concentration of hydrogen ions in a solution and is therefore an organic acid?
D
The complexity and variety of organic molecules is due to
the chemical versatility of carbon atoms.
Which of the following statements correctly describes cis–trans isomers?
They have variations in arrangement around a double bond.
Which molecule shown above contains a functional group that cells use to transfer energy between organic molecules?
D
Why are hydrocarbons insoluble in water?
The majority of their bonds are nonpolar covalent carbon–to–hydrogen linkages.
Which functional groups can act as acids?
carboxyl and phosphate
Which molecule shown above contains an amino functional group, but is not an amino acid?
A
A chemist wishes to make an organic molecule less acidic. Which of the following functional groups should be added to the molecule in order to do so?
amino
Amino acids are acids because they always possess which functional group?
carboxyl
Thalidomide and L–dopa, shown below, are examples of pharmaceutical drugs that occur as enantiomers, or molecules that
are mirror images of one another.
Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, a hydrocarbon chain with the same number of carbon atoms, but with one or more double bonds, will
be more constrained in structure.
Which molecule shown above has a carbonyl functional group in the form of a ketone?
C
Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that
are mirror images of one another.
Which of the groups shown above is a functional group that helps stabilize proteins by forming covalent cross–links within or between protein molecules?
E
Which functional group is not present in this molecule?
sulfhydryl
Testosterone and estradiol are
structural isomers of each other.
A carbon atom is most likely to form what kind of bond(s) with other atoms?
covalent
What is the name of the functional group shown in the figure above?
carboxyl
Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?
Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers.
The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. What is the result of adding hydrogens to vegetable oil?
The hydrogenated vegetable oil stays solid at room temperature.
Which bonds are created during the formation of the primary structure of a protein?
peptide bonds
Which of the following is true regarding saturated fatty acids?
They are the principal molecules in lard and butter.
How many molecules of water are needed to completely hydrolyze a polymer that is 11 monomers long?
10
The molecule shown in Figure 5.3 is a
unsaturated fatty acid.
Which of the following is not a monomer/polymer pairing?
triglyceride/phospholipid bilayer
Why are human sex hormones considered to be lipids?
They are not soluble in water.
All of the following contain amino acids except
cholesterol
Which of these classes of biological molecules consist of both small molecules and macromolecular polymers?
carbohydrates
The bonding of two amino acid molecules to form a larger molecule requires
the release of a water molecule.
What aspects of protein structure are stabilized or assisted by hydrogen bonds?
secondary, tertiary, and quaternary structures, but not primary structure
At which level of protein structure are interactions between the side chains (R groups) most important?
tertiary
Changing a single amino acid in a protein consisting of 325 amino acids would
always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and affect its biological activity.
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?
C18H32O16
The tertiary structure of a protein is the
unique three–dimensional shape of the fully folded polypeptide.
Humans and mice differ because
their cells have some differences in the sequence of nucleotides in their nucleic acids.
Which of the following statements concerning saturated fats is not true?
They have multiple double bonds in the carbon chains of their fatty acids.
Which of the following is not a polymer?
glucose
There are 20 different amino acids. What makes one amino acid different from another?
different side chains (R groups) attached to an á carbon
Note
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