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25/11/2024 13:32PM
BIOC 3021 EXAM 1 REVIEW SHEETS
SOLUTIONS
What are the six most common elements present as covalent components of bioorganic
compounds? - Answers✓✓H, O, N, C, S, P, Cl
What are covalent bonds, and how strong and permanent are they relative to other bonds in
living organisms? - Answers✓✓Covalent bonds are the sharing of electrons between two
species. Non polar covalent bonds are the strongest
What is the difference between polar and nonpolar covalent bonds? What combinations of
atoms are involved in these two kinds of covalent bonds? - Answers✓✓Polar covalent bonds:
The EN differs (C-O bonds)
Non-polar covalent bonds: En is identical or is very similar (H-H bonds)
What are common ionic elements in biological systems? What happens to ionic substances in
the aqueous environment of living organisms? What are the properties of the ionic bonds that
occur between inorganic ions or between organic ions? - Answers✓✓Common ionic elements:
Na and Cl
In aqueous environments ionic substances dissociate
Inorganic compounds form ionic bonds that have high melting points that are made up of a
single element or compound that does not include carbon or hydrogen.
What are hydrogen bonds? What organic structures are involved in hydrogen bonding? What is
the importance of hydrogen bonding in living organisms? - Answers✓✓Hydrogen bonds are
polar bonds that have a partially positive H interacting with a partially negative element (like O
, ©Themoon EXAM SOLUTIONS
25/11/2024 13:32PM
or N). Important because they are essential for protein structure, binding of enzymes to
substrate and they hold the DNA helixx together.
What are two types of nonpolar bonds? Why do nonpolar molecules aggregate together in
water? - Answers✓✓Van der waals forces and hydrophobic interactions
Van der Waals forcesCaused by induced electrical interactions between closely approaching
atoms
E clouds fluctuate together to "fit together"
Strength depends on size of atoms and the distance
Bigger e- clouds from stronger interactions
Strength is inversely proportional to the 6th power of distance
Atoms need to be 2nm apart
Hydrophobic Interactions
These bonds form due to exclusion of water from groups of non polar molecules
Water molecules prefer each other (strongest interactions)
Forces nonpolar molecules together
Hydrophobic molecules are not really attracted to each other, they just herded together by water
so that the maximum number of water-water interactions can form
Water molecules push hydrophobic molecules together so that fewer water molecules need to
be near hydrophobic molecules, water water H bonding can be maximized
What is pH and how does it relate to the molarity of hydrogen ions in solution? -
Answers✓✓pH is the numerical value of -log[H+]. It describes the solutions acidity It is
inversely related to the hydrogen ion concentration. So if pH decreases then H ion increases
tenfold.
What is a strong acid? What is the percent dissociation of a strong acid in water? When a strong
acid is present in water, why are the molarity of the strong acid and the molarity of the
, ©Themoon EXAM SOLUTIONS
25/11/2024 13:32PM
hydrogen ion the same? - Answers✓✓A strong Acid completely dissociates in water. The
concentrations of Hydrogen ion and acid are equal since it dissociates completely in an aqueous
environment.
What is a weak acid, and why are weak acids not completely dissociated? Why are the molarity
of the weak acid and the molarity of the hydrogen ion not the same? If a 0.1 M solution of a
weak acid is 10% dissociated, what is the molarity of hydrogen ions? - Answers✓✓Weak Acid
does not dissociate completely in water. Molarities are not the same due to the lack of complete
dissociation.
0.1M x (10/100)= 0.01 M
What is a buffer solution? Why is a mixture of a weak acid and its conjugate base needed to
give good buffering? Why doesn't a solution containing just a weak acid serve as a buffer? Why
don't strong acids serve as buffers? - Answers✓✓A buffer solution consists of a weak acid and
its conjugate base equilibrium in an aqueous solvent. It can resist changes in pH when a strong
acid or strong base is added. Can't have just one because then the equation would only go one
way. A strong acid can't be a buffer because it ionizes completely.
Write the Henderson-Hasselbach equation. What are the definitions of pH, pKa and log A-
/HA? Why do all weak acids give the same shaped titration curve? At what pH does a weak
acid and conjugate base combination give the best buffering? If a weak acid has a pKa of 5
what is the pHwhen the weak acid is 10%, 50% and 90% titrated with NaOH? -
Answers✓✓pH=pKA+log[A-]/[HA]. pH describes the solution acidity as it is the numerical
value of -log[H+].pKa is the strength of an acid. Log a-/HA is the molar concentration of the
conjugate base. All have the same titration curve because it has the same flat region +/- 1 unit
from pKa, give the best buffering at pH that is -/+1 from pKa
PH=4.05, 5, 5.95
If the pKa is 6 and the ratio of A-/HA is 1 what is the pH? If the pKa is 6 and the ratio of A-
/HA is 10 what is the pH? If the pKa is 6 and the pH is 6 what is the ratio of A-/HA? If the pKa
is 6 and the pH is 5 what is the ratio A-/HA? - Answers✓✓6,7,1,0.01
25/11/2024 13:32PM
BIOC 3021 EXAM 1 REVIEW SHEETS
SOLUTIONS
What are the six most common elements present as covalent components of bioorganic
compounds? - Answers✓✓H, O, N, C, S, P, Cl
What are covalent bonds, and how strong and permanent are they relative to other bonds in
living organisms? - Answers✓✓Covalent bonds are the sharing of electrons between two
species. Non polar covalent bonds are the strongest
What is the difference between polar and nonpolar covalent bonds? What combinations of
atoms are involved in these two kinds of covalent bonds? - Answers✓✓Polar covalent bonds:
The EN differs (C-O bonds)
Non-polar covalent bonds: En is identical or is very similar (H-H bonds)
What are common ionic elements in biological systems? What happens to ionic substances in
the aqueous environment of living organisms? What are the properties of the ionic bonds that
occur between inorganic ions or between organic ions? - Answers✓✓Common ionic elements:
Na and Cl
In aqueous environments ionic substances dissociate
Inorganic compounds form ionic bonds that have high melting points that are made up of a
single element or compound that does not include carbon or hydrogen.
What are hydrogen bonds? What organic structures are involved in hydrogen bonding? What is
the importance of hydrogen bonding in living organisms? - Answers✓✓Hydrogen bonds are
polar bonds that have a partially positive H interacting with a partially negative element (like O
, ©Themoon EXAM SOLUTIONS
25/11/2024 13:32PM
or N). Important because they are essential for protein structure, binding of enzymes to
substrate and they hold the DNA helixx together.
What are two types of nonpolar bonds? Why do nonpolar molecules aggregate together in
water? - Answers✓✓Van der waals forces and hydrophobic interactions
Van der Waals forcesCaused by induced electrical interactions between closely approaching
atoms
E clouds fluctuate together to "fit together"
Strength depends on size of atoms and the distance
Bigger e- clouds from stronger interactions
Strength is inversely proportional to the 6th power of distance
Atoms need to be 2nm apart
Hydrophobic Interactions
These bonds form due to exclusion of water from groups of non polar molecules
Water molecules prefer each other (strongest interactions)
Forces nonpolar molecules together
Hydrophobic molecules are not really attracted to each other, they just herded together by water
so that the maximum number of water-water interactions can form
Water molecules push hydrophobic molecules together so that fewer water molecules need to
be near hydrophobic molecules, water water H bonding can be maximized
What is pH and how does it relate to the molarity of hydrogen ions in solution? -
Answers✓✓pH is the numerical value of -log[H+]. It describes the solutions acidity It is
inversely related to the hydrogen ion concentration. So if pH decreases then H ion increases
tenfold.
What is a strong acid? What is the percent dissociation of a strong acid in water? When a strong
acid is present in water, why are the molarity of the strong acid and the molarity of the
, ©Themoon EXAM SOLUTIONS
25/11/2024 13:32PM
hydrogen ion the same? - Answers✓✓A strong Acid completely dissociates in water. The
concentrations of Hydrogen ion and acid are equal since it dissociates completely in an aqueous
environment.
What is a weak acid, and why are weak acids not completely dissociated? Why are the molarity
of the weak acid and the molarity of the hydrogen ion not the same? If a 0.1 M solution of a
weak acid is 10% dissociated, what is the molarity of hydrogen ions? - Answers✓✓Weak Acid
does not dissociate completely in water. Molarities are not the same due to the lack of complete
dissociation.
0.1M x (10/100)= 0.01 M
What is a buffer solution? Why is a mixture of a weak acid and its conjugate base needed to
give good buffering? Why doesn't a solution containing just a weak acid serve as a buffer? Why
don't strong acids serve as buffers? - Answers✓✓A buffer solution consists of a weak acid and
its conjugate base equilibrium in an aqueous solvent. It can resist changes in pH when a strong
acid or strong base is added. Can't have just one because then the equation would only go one
way. A strong acid can't be a buffer because it ionizes completely.
Write the Henderson-Hasselbach equation. What are the definitions of pH, pKa and log A-
/HA? Why do all weak acids give the same shaped titration curve? At what pH does a weak
acid and conjugate base combination give the best buffering? If a weak acid has a pKa of 5
what is the pHwhen the weak acid is 10%, 50% and 90% titrated with NaOH? -
Answers✓✓pH=pKA+log[A-]/[HA]. pH describes the solution acidity as it is the numerical
value of -log[H+].pKa is the strength of an acid. Log a-/HA is the molar concentration of the
conjugate base. All have the same titration curve because it has the same flat region +/- 1 unit
from pKa, give the best buffering at pH that is -/+1 from pKa
PH=4.05, 5, 5.95
If the pKa is 6 and the ratio of A-/HA is 1 what is the pH? If the pKa is 6 and the ratio of A-
/HA is 10 what is the pH? If the pKa is 6 and the pH is 6 what is the ratio of A-/HA? If the pKa
is 6 and the pH is 5 what is the ratio A-/HA? - Answers✓✓6,7,1,0.01
