Biochemistry Module Exam 1 WITH
VERIFIED ANSWERS 100%
What is the formula used to calculate pH? - Correct answer- pH = -log[H+]
If you have a solution that is a pH of 3.6, what is the pOH and what is pOH measuring? - Correct
answer- pH + pOH = 14
The pOH would be 10.4. Similar to pH, the pOH measures the hydroxyl ion concentration in
solution
If a solution is acidic then you would expect there to be few OH- ions and thus present in a very
low concentration. A pOH of 10.4 is equal to [OH-] = 4 x 10^-11 M
Why is pure water neutral and at a pH = 7? - Correct answer- In freshly distilled water, there is
an equal concentration of [H^+] and [OH^-].
With increasing CO2 concentration in the atmosphere what would you expect would happen to
the pH of lakes, rivers, and oceans? - Correct answer- One would predict the large bodies of
water to equilibrate with atmospheric CO_2 and become more acidic.
Sea water is about ______________ times more basic than black coffee. - Correct answer- 1,000
What is the pH range of blood? - Correct answer- 7.35-7.45
, For a solution of the weak acid HA, what are the formulas used to calculate Ka = ____________
and pKa = ____________? - Correct answer- Ka = [H+][A-] / [HA]
pKa = -log [Ka]
The pK of acetic acid is pK = 4.76. For a 0.1 M solution of acetic acid at a pH = 4.76 what is the
concentration of [H+]? - Correct answer- [H+] = [CH3COO-] = 0.05 M. For solutions of weak acids
and bases with a pH = pK the concentrations of H+ and OH- are equal.
Write the Henderson-Hasselbalch equation. - Correct answer- pH = pKa + log([A-]/[HA])
Why are weak acids and bases good buffers and how does a buffer work? - Correct answer-
Weak acids and bases only partially dissociate into H+ and conjugate base. They are good
buffers because in solution there is a pH = pK at which the weak acid or base is only 50%
dissociated and could donate or accept hydrogen ions if a reaction in the solution used or
created more H+. Buffers work by accepting or donating H+, when at pH = pK and preventing
rapid changes in the solution pH
What are the three major buffering systems used in our bodies? - Correct answer- Phosphate,
proteins, bicarbonate
When we exercise we produce CO2 and lactic acid in our muscle tissues. How do our bodies
prevent wide fluctuations in blood pH from exercise? - Correct answer- The bicarbonate buffer
helps to maintain a constant blood pH but because its pK is over 1 pH unit from the blood pH
7.4. Because of this our bodies have evolved a complex system to prevent build up of CO2
concentrations in blood by expiring the excess CO2 from our lungs and by excreting it in our
urine
VERIFIED ANSWERS 100%
What is the formula used to calculate pH? - Correct answer- pH = -log[H+]
If you have a solution that is a pH of 3.6, what is the pOH and what is pOH measuring? - Correct
answer- pH + pOH = 14
The pOH would be 10.4. Similar to pH, the pOH measures the hydroxyl ion concentration in
solution
If a solution is acidic then you would expect there to be few OH- ions and thus present in a very
low concentration. A pOH of 10.4 is equal to [OH-] = 4 x 10^-11 M
Why is pure water neutral and at a pH = 7? - Correct answer- In freshly distilled water, there is
an equal concentration of [H^+] and [OH^-].
With increasing CO2 concentration in the atmosphere what would you expect would happen to
the pH of lakes, rivers, and oceans? - Correct answer- One would predict the large bodies of
water to equilibrate with atmospheric CO_2 and become more acidic.
Sea water is about ______________ times more basic than black coffee. - Correct answer- 1,000
What is the pH range of blood? - Correct answer- 7.35-7.45
, For a solution of the weak acid HA, what are the formulas used to calculate Ka = ____________
and pKa = ____________? - Correct answer- Ka = [H+][A-] / [HA]
pKa = -log [Ka]
The pK of acetic acid is pK = 4.76. For a 0.1 M solution of acetic acid at a pH = 4.76 what is the
concentration of [H+]? - Correct answer- [H+] = [CH3COO-] = 0.05 M. For solutions of weak acids
and bases with a pH = pK the concentrations of H+ and OH- are equal.
Write the Henderson-Hasselbalch equation. - Correct answer- pH = pKa + log([A-]/[HA])
Why are weak acids and bases good buffers and how does a buffer work? - Correct answer-
Weak acids and bases only partially dissociate into H+ and conjugate base. They are good
buffers because in solution there is a pH = pK at which the weak acid or base is only 50%
dissociated and could donate or accept hydrogen ions if a reaction in the solution used or
created more H+. Buffers work by accepting or donating H+, when at pH = pK and preventing
rapid changes in the solution pH
What are the three major buffering systems used in our bodies? - Correct answer- Phosphate,
proteins, bicarbonate
When we exercise we produce CO2 and lactic acid in our muscle tissues. How do our bodies
prevent wide fluctuations in blood pH from exercise? - Correct answer- The bicarbonate buffer
helps to maintain a constant blood pH but because its pK is over 1 pH unit from the blood pH
7.4. Because of this our bodies have evolved a complex system to prevent build up of CO2
concentrations in blood by expiring the excess CO2 from our lungs and by excreting it in our
urine
