session 10 practice problems

do not yield ions when dissolved in water

non-electrolytes

a dynamic state in which the rate of the forward reaction is equal to the rate of the reverse reaction

equilibrium

a molecule that is electrically neutral but has nonadjacent regions of negative and positive charge

zwitterion

a solution with a pH greater than 7.0

basic

this has been experimentally determined to be 1 × 10^(-14) M^2 at 25 ºC

ion product constant

dissociate completely (or nearly completely) into ions in aqueous solutions

strong electrolytes

a solution with a pH less than 7.0

acidic

refers to the fact that pure water contains a very small amount of hydronium and hydroxide ions in solution due to proton transfer between two molecules of water

autoionization

only partially dissociate into ions in aqueous solutions

weak electrolytes

the negative log of the molar concentration of hydronium ions in solution

pH

What is the pH of a 0.0375 M solution of barium hydroxide (Ba(OH)₂)? Note that barium hydroxide is a strong base and dissociates (ionizes) completely in water. Refer to the image below.

Enter your answer to nearest tenths decimal place.

12.9

Rank the following aqueous solutions from most acidic to least acidic? The hydronium [H₃O⁺] ion concentrations for each solution are provided.

(MOST ACIDIC) - Solution X, Solution Z, Solution W, Solution Y - (LEAST ACIDIC)

In general, unionized drugs are more water soluble and ionized drugs are more lipid soluble.

 

True

 

False

false

The majority of drug absorption takes place in the small intestine.

 

True

 

False

true

The absorption of a weak electrolyte is primarily determined by the extent to which the drug exists in its unionized (neutral) form at the absorption site.

 

True

 

False

true

Which form of the drug naproxen will be more water soluble? Refer to the image below.

 

Water solubility will be equivalent for both forms

 

Ionized (charged) form

 

Acid (neutral) form

Ionized (charged) form

Which form of the drug fluoxetine will be more lipid soluble?

 

Ionized (charged) form

 

Water solubility will be equivalent for both forms

 

Base (neutral) form

Base (neutral) form

Amphoteric compounds are molecules that can function as either weak acids or weak bases in aqueous solutions.

 

True

 

False

True

The largest category of ionizable drugs are single acids.

 

True

 

False

False

The degree to which weak electrolyte drugs are ionized has extensive physiological implications.

 

True

 

False

True

What is the pH of a 0.02335 M solution of calcium hydroxide (Ca(OH₂))? Note that calcium hydroxide is a strong base and dissociates (ionizes) completely in water. 

Enter your answer to nearest tenths decimal place.

12.7

What is the pOH of a solution with a hydronium ion [H₃O]⁺ concentration of 6.4 x 10^-6 M?

Enter your answer to nearest tenths decimal place.

8.81

What is the pH of a 0.043 M solution of trifluoroacetic acid? Note that trifluoroacetic acid is a strong acid and dissociates (ionizes) completely in water.

Enter your answer to nearest tenths decimal place.

1.37

Magnesium hydroxide (Mg(OH)₂) is a strong base and dissociates (ionizes) completely in water as shown in the image below.  What is the pH of a 0.00245 M solution of magnesium hydroxide?

Enter your answer to the nearest tenths decimal place.

11.7

Identify all of the FALSE statements. 

 

The absorption of a weak electrolyte is primarily determined by the extent to which the drug exists in its unionized (neutral) form at the absorption site.

 

pH is defined as the negative log of the mole fraction of hydronium ions in solution.

 

Amphoteric compounds are molecules that can function as either weak acids or weak bases in aqueous solutions.

 

The majority of drug absorption takes place in the stomach.

 

In general, ionized drugs are more water soluble and unionized drugs are more lipid soluble.

pH is defined as the negative log of the mole fraction of hydronium ions in solution

The majority of drug absorption takes place in the stomach

Shown below are the hydronium [H₃O⁺] ion concentrations for three different solutions. Rank the three solutions according to acidity.

Solution A	Solution B	Solution C
3.3 x 10-5 M	2.7 x 10-4 M	1.6 x 10-6 M

least: C

intermediate: A

most: B

Hydrochloric acid (HCl) is a strong electrolyte and dissociates (ionizes) completely in water. The image below shows the dissociation reaction of HCl in water. What is the pH of a 0.075 M solution of aqueous HCl? 

 Enter your answer to the nearest tenths decimal place.

1.1

While pH Partition Theory is a useful conceptual framework for considering drug absorption, it is an oversimplification and has some limitations. Choose the word that best completest the following three statements detailing such limitations.

• The small intestine has a ___ surface area that can compensate for ionization effects.

• Some drugs have relatively ____ residence times that also compensate for ionization effects

• Some drugs are _____ via active rather than passive transport.

large; long; absorbed

Choose the best word(s) to complete the following sentence.

Autoionization refers to the fact that pure water contains a very small amount of hydronium (H₃O⁺] and hydroxide (^-OH) ions in solution due to _________ between two molecules of water.

proton transfer