Q: If the pH of a solution is 4, what is the concentration of hydronium ions $$[\mathrm{H^+}]$$?

$$1 \times 10$$^{-4}$$\ \mathrm{M}$$

Question 1

Which property of water is primarily responsible for its ability to dissolve ionic compounds such as NaCl?

Accepted Answer

Its polarity and ability to form hydrogen bonds

Question 2

How many hydrogen bonds can a single water molecule form with neighboring water molecules?

Accepted Answer

Four

Question 3

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil is nonpolar and cannot form hydrogen bonds with water

Question 4

Given the ionization of water: $$2\ \mathrm{H_2O} \rightleftharpoons \mathrm{H_3O^+} + \mathrm{OH^-}$$, what is the value of $$K_w at 25$$°C?

Accepted Answer

$$1 	imes 10$$^{-14}$$

Question 5

If the pH of a solution is 4, what is the concentration of hydronium ions $$[\mathrm{H^+}]$$?

Accepted Answer

$$1 	imes 10$$^{-4}$$\ \mathrm{M}$$

Question 6

Lemon juice has a pH of 2 and beer has a pH of 4. How many times more acidic is lemon juice compared to beer?

Accepted Answer

100 times

Question 7

Which equation correctly relates pH, pKa, and the ratio of conjugate base to acid in a buffer system?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[\mathrm{A}^-]}{[\mathrm{HA}]} \right)$$

Question 8

A buffer is prepared with $$0.1\ \mathrm{M}$$ acetic acid and $$0.6\ \mathrm{M}$$ acetate. If $$K_a = 1.8 	imes 10$$^{-5}$$, what is the pH of the buffer? (Use $$\mathrm{p}K_a = 4.7$$)

Accepted Answer

pH = 5.48

Question 9

Which of the following best describes the role of a buffer in biological systems?

Accepted Answer

It resists changes in pH when small amounts of acid or base are added

Question 10

Which of the following statements about the relationship between pH and pKa is correct?

Accepted Answer

When pH = pKa, $$[\mathrm{HA}] = [\mathrm{A}^-]$$

Question 11

A patient with severe diabetes is found to have a blood pH of 7.1. What condition does this indicate?

Accepted Answer

Acidosis

Question 12

Which of the following molecules is amphipathic and can form micelles in water?

Accepted Answer

Phospholipid

Question 13

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice create an open lattice structure

Question 14

Which of the following is true regarding the effect of adding a strong base to a buffered solution compared to an unbuffered solution?

Accepted Answer

The pH of the buffered solution changes only slightly

Question 15

Which of the following is the correct expression for the ion product of water ($$K_w$$)?

Accepted Answer

$$K_w = [\mathrm{H^+}][\mathrm{OH^-}]$$

Question 16

Which of the following amino acids is most effective as a buffer near physiological pH (7.4)?

Accepted Answer

Histidine (pKa = 6.0)

Question 17

Which of the following best describes a conjugate acid-base pair?

Accepted Answer

An acid and its corresponding base that differ by one proton

Question 18

Which of the following is a real-life application of the Henderson-Hasselbalch equation in medicine?

Accepted Answer

Determining the pH of blood using bicarbonate and CO$$_2$$ concentrations

Question 19

If a solution has $$[\mathrm{OH^-}] = 1 	imes 10$$^{-9}$$\ \mathrm{M}$$, what is its pH?

Accepted Answer

pH = 5

Question 20

Which of the following statements about acids and bases is correct?

Accepted Answer

A weak acid has a low tendency to donate protons

Water, Acids, Bases, and Buffer Systems in Biochemistry

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