Acid-Base Theory and Solubility Quiz

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Questions and Answers

What is a common component of elixirs that is responsible for providing sweetness?

Alcohol

Preservatives

Artificial sweeteners (correct)

Glycerin

Which of the following is NOT a step in the preparation of elixirs?

Completing to volume with an appropriate solvent

Dissolving components separately in alcohol and water

Combining aqueous and alcoholic solutions

Storing in a glass container at room temperature (correct)

When diluting a medicated elixir to create a non-medicated elixir, which factor must be equally maintained?

The color of the elixirs

The volume of preservatives used

The alcohol content (correct)

The flavor intensity of the elixir

Which of the following is essential for flavoring agents in elixirs?

Always being used Signup and view all the answers

What characteristic of the storage container for elixirs is critical?

Must be tight and light-resistant Signup and view all the answers

Which of the following is an example of a buffering agent used in solid oral dosage forms?

Phosphoric acid buffer Signup and view all the answers

What is the primary purpose of tonicity adjusters?

To render a solution similar in osmotic pressure to physiological fluids Signup and view all the answers

Which of the following best describes single-phase liquid systems?

They have completely dissolved drug substances Signup and view all the answers

What is a notable disadvantage of single-phase oral systems?

Bulky compared to solid dosage forms Signup and view all the answers

Which single-phase liquid form is characterized as having drug substances dissolved in a suitable solvent?

All of the above Signup and view all the answers

What is one key feature of solutions in single-phase liquid systems?

Complete dissolution of the drug Signup and view all the answers

What percentage of aspirin is un-ionized in the stomach at pH 1 if its pKa is 3.5?

99.7% Signup and view all the answers

Which of the following is NOT typically a concern with single-phase oral systems?

Rapid absorption Signup and view all the answers

Which agent is commonly used as a tonicity adjuster for injectable products?

Sodium chloride Signup and view all the answers

At what pH is a weak acid almost completely ionized?

When pH is 2 units above its pKa Signup and view all the answers

Which statement accurately describes the behavior of NH3 in relation to pH and ionization?

NH3 becomes ionized when the pH is 2 units below its pKa. Signup and view all the answers

What happens to a weak acid like acetic acid (CH3COOH) when the pH is decreased significantly?

It stays un-ionized until the pH is increased. Signup and view all the answers

When considering weak bases, what occurs when the pH is 2 units below the pKa?

The weak base is exclusively ionized. Signup and view all the answers

Which factor does NOT affect the ionization of weak acids and bases?

Temperature of the solution Signup and view all the answers

What is the relationship between pH and pKa for weak acids and bases?

Weak acids are more un-ionized at pH above their pKa. Signup and view all the answers

If the pH of a solution is increased significantly, what would happen to a weak acid?

The weak acid would become more ionized. Signup and view all the answers

Which of the following compounds has the highest solubility in water based on the given data?

Chlordiazepoxide Maleate Signup and view all the answers

What is the relationship between Ka and Kb in conjugate acid-base pairs?

Ka x Kb = 10^-14 Signup and view all the answers

Given the formula pKA = -log10(KA), what is the pKA of NH4+ if its KA is 5.75 x 10^-10?

9.26 Signup and view all the answers

Which statement is true regarding weak bases?

Weak bases have a finite Kb. Signup and view all the answers

What characterizes a strong base in terms of Kb?

Kb is infinite. Signup and view all the answers

Which functional groups are typically characteristic of weakly basic drugs?

Aliphatic amines Signup and view all the answers

What does a larger [HA] and smaller Ka indicate about a weak acid?

It is less dissociated. Signup and view all the answers

Which type of ammonium salt is not classified as a weak base?

Quaternary ammonium salts Signup and view all the answers

What is the primary function of thickeners in pharmaceutical formulations?

To increase the viscosity and improve mouth feel Signup and view all the answers

Which of the following is a characteristic of dye-free formulations?

Designed for patients with allergies to artificial colors Signup and view all the answers

Which colorant is an example of a synthetic dye that may cause allergic reactions?

FD&C Yellow #5 Signup and view all the answers

What role do solubilizing agents play in formulations?

They help solubilize poorly water-soluble drugs Signup and view all the answers

Which of the following is NOT an example of an acidifying agent?

Diethanolamine Signup and view all the answers

Buffer systems in liquid preparations serve what primary purpose?

To resist changes in pH when acid or base is added Signup and view all the answers

What is a common example of a natural thickener used in pharmaceutical formulations?

Xanthan gum Signup and view all the answers

Which statement about colorants is true regarding their relationship with flavor?

Color should typically correspond with the flavor being employed Signup and view all the answers

What is a characteristic that typically distinguishes elixirs from syrups?

Elixirs are less effective in masking the taste of medicinal substances. Signup and view all the answers

What should one assume when encountering the term 'elixir' on a product label?

The product contains at least 10% alcohol. Signup and view all the answers

What is one of the major disadvantages of using alcohol in elixirs?

It can lead to inebriation. Signup and view all the answers

How do 'iso-alcoholic elixirs' differ from traditional elixirs?

They are made by mixing low and high alcoholic elixirs. Signup and view all the answers

What is a common marketing practice regarding alcoholic elixirs that have been reformulated?

They are often renamed to reflect their new formulation accurately. Signup and view all the answers

What happens when a supersaturated solution is disturbed by shaking or adding a seed crystal?

It results in spontaneous precipitation or crystallization. Signup and view all the answers

What is the classification of a solute that dissolves less than 1 part in 1 part of solvent?

Very soluble Signup and view all the answers

Which expression correctly describes solubility?

The maximum concentration of solute that can dissolve in a solvent at a particular temperature. Signup and view all the answers

Which of the following shows the correct calculation for determining the percentage concentration (%w/v) of a NaCl solution?

(1g / 2.8mL) x 100mL = 36% w/v Signup and view all the answers

Which term best describes a solute that has a solubility of more than 10,000 mL to dissolve 1 mg of substance?

Practically insoluble Signup and view all the answers

How is molarity expressed in a solution?

moles of solute per liter of solution Signup and view all the answers

What is the significance of the information provided by USP/NF regarding solubility?

It specifies the volume of solvent required to dissolve a gram of solute. Signup and view all the answers

If a solute's defined solubility is less than 1 part in 1 part of solvent, what term can be used to describe it?

Very soluble Signup and view all the answers

What is one significant advantage of formulating drugs as salts of weak bases?

Improved stability during storage Signup and view all the answers

How should different salts of the same active drug be treated in terms of their properties?

They exhibit distinct chemical and biological properties Signup and view all the answers

Which of the following is a common issue faced with weak bases like amines?

Volatility and instability Signup and view all the answers

In a buffer solution, what does a higher concentration of sodium borate relative to boric acid indicate?

An increase in pH Signup and view all the answers

What is the effect of a drug being formulated as a hydrochloride salt?

It improves handling during processing Signup and view all the answers

When calculating the ionization of a weak base, what does the formula reveal at a pH lower than its pKa?

Un-ionized form predominates Signup and view all the answers

Which of the following borate compounds is typically used for buffering?

A mixture of boric acid and sodium borate Signup and view all the answers

What could be an implication of choosing a less soluble salt for oral calcium supplements?

Decreased efficacy in providing calcium Signup and view all the answers

What is the primary purpose of selecting different salt forms of the same drug?

To enhance the drug's bioavailability or stability Signup and view all the answers

Which factor is most likely to change when a weak base is converted to its salt form?

Chemical and biological properties Signup and view all the answers

What is the primary purpose of polyhydric alcohols in syrup formulations?

Retard crystallization Signup and view all the answers

When is the solution with heat method typically preferred for preparing syrups?

To achieve faster dissolution of components Signup and view all the answers

What is a disadvantage of using heat in syrup preparation?

Inversion of sucrose to glucose and fructose Signup and view all the answers

What is the main characteristic of the agitation without heat method in syrup preparation?

It results in a more stable final product Signup and view all the answers

Which of the following is considered a buffering agent in solid oral dosage forms?

Citric acid Signup and view all the answers

Which process involves allowing purified water to pass through crystalline sucrose?

Percolation Signup and view all the answers

Which of the following methods for syrup preparation is the most time-consuming?

Agitation without heat Signup and view all the answers

What is the primary role of tonicity adjusters in pharmaceutical products?

To ensure a solution's osmotic pressure is similar to physiological fluids Signup and view all the answers

What is the main effect of using thickeners in syrup formulations?

Minimize contact with taste buds Signup and view all the answers

Which of the following represents a disadvantage of single-phase oral systems?

Potential taste issues Signup and view all the answers

Which of the following describes a characteristic of single-phase liquid systems?

They consist of completely dissolved drug substances in a solvent Signup and view all the answers

What risk is associated with incorporating heat-labile substances into syrup during preparation?

They may volatize and alter the taste Signup and view all the answers

In what context are boric acid and sodium chloride typically used?

As tonicity adjusters Signup and view all the answers

Which component is crucial for achieving a stable syrup without heat?

Agitation for extended periods Signup and view all the answers

What purpose do solubilizing agents serve in syrup formulations?

They improve the dissolution of insoluble substances Signup and view all the answers

Which of the following is an advantage of single-phase oral systems?

More flexible dosing options Signup and view all the answers

What is a common characteristic of solutions within single-phase liquid systems?

Uniform dispersion of drug throughout the solvent Signup and view all the answers

What type of liquid preparations includes solutions, syrups, and tinctures?

Single-phase liquid systems Signup and view all the answers

Which of the following is NOT true about single-phase oral systems?

They require shaking to ensure uniformity of dose Signup and view all the answers

Which ingredient serves as a tonicity adjuster but can also act as a buffering agent in formulations?

Boric acid Signup and view all the answers

What is the primary reason weak electrolytes only partially ionize in solution?

Their dissociation is an equilibrium process. Signup and view all the answers

Which statement best describes the role of a co-solvent in a solution?

It increases the solubility of non-polar substances. Signup and view all the answers

What property of a solvent is primarily influenced by temperature changes?

The solubility of solutes generally increases. Signup and view all the answers

Which of the following best describes a primary function of taste masking agents in pharmaceutical formulations?

To obscure unpleasant tastes of active ingredients. Signup and view all the answers

How does temperature typically affect the solubility of a gas in a liquid?

Gas solubility decreases with rising temperature. Signup and view all the answers

Which characteristic of an electrolyte determines its strength in solution?

The number of ions it produces. Signup and view all the answers

Which factor contributes to the effectiveness of a buffer in maintaining pH levels?

The concentration of acid and conjugate base present. Signup and view all the answers

What is the primary purpose of an excipient in a buffered solution?

To stabilize the pH of the solution. Signup and view all the answers

What is the likely taste of a drug prepared as a free base?

Bitter Signup and view all the answers

What is one potential advantage of using a co-solvent system for oral dosage forms?

Improved solubility of poorly soluble drugs Signup and view all the answers

When preparing a solution requiring a small volume of an ingredient, such as 0.2 mL of peppermint oil, what is the most efficient measuring approach if only larger measuring devices are available?

Dilute the ingredient and use aliquots Signup and view all the answers

Which of the following statements regarding weak electrolytes is accurate?

They partially dissociate in solution. Signup and view all the answers

What is the correct classification of sodium phenytoin?

Salt of a weak acid Signup and view all the answers

Which of the following best describes the behavior of strong bases in terms of their dissociation in water?

Completely dissociate into ions. Signup and view all the answers

Which of the following substances is recognized as a weak base?

Ammonia Signup and view all the answers

What is the expected pH of a 0.1 M solution of potassium acetate given that Ka = 1.75 x 10^-3?

6.38 Signup and view all the answers

Which property of solvents plays a critical role in the solubility of substances?

Polarity Signup and view all the answers

When the concentration of a weak acid decreases, how is the ionization affected?

Decreases overall. Signup and view all the answers

What is the expected solubility of caffeine at 25^o^C if its solubility at 80^o^C is 0.167 g/ml?

0.146 g/mL Signup and view all the answers

Which statement about the properties of solvents is true?

Glycerin is often used as a humectant within otic solutions. Signup and view all the answers

Which agent may be used to mask taste by anesthetizing the taste buds?

Menthol Signup and view all the answers

What are two potential advantages of using a co-solvent system to prepare solution dosage forms?

Increased drug solubility and improved stability. Signup and view all the answers

How does the solubility behavior of electrolytes differ from that of non-electrolytes in solutions?

Electrolytes dissociate into ions, affecting colligative properties. Signup and view all the answers

What is the expected solubility of caffeine if its solubility is 0.167 g/ml at 80°C and must be evaluated at 25°C?

Decreases significantly Signup and view all the answers

Which of these characteristics describes exothermic materials in relation to drug solutions?

Releases heat during dissolution Signup and view all the answers

In the context of a 75:25 water:glycerin co-solvent system, what is the maximum solubility achievable for a drug with solubility of 2.5 mg/ml in water and 20 mg/ml in glycerin?

4.2 mg/ml Signup and view all the answers

When preparing a drug solution in a 50:25:25 water:glycerin:Alcohol, USP co-solvent system, how does the solubility of the drug change based on the solvent composition?

Depends on the combined effect of all solvents Signup and view all the answers

Which option best describes the solubility behavior of electrolytes when mixed in different solvent systems?

Varies based on solvent polarity Signup and view all the answers

What is a common advantage of utilizing co-solvent systems in pharmaceutical formulations?

Enhances drug solubility Signup and view all the answers

With a solubility of 1.4 mg/ml in water and 91 mg/ml in ethanol, what percentage of ethanol must be used to achieve a 1.5% solution of phenobarbital?

43% water, 57% ethanol Signup and view all the answers

Which of the following properties should be considered when choosing solvents for drug formulation?

Taste masking capabilities Signup and view all the answers

In a mixture of glycerin and water, how is the overall dielectric constant estimated if glycerin is at 40% concentration?

It is a linear combination of both constants Signup and view all the answers

What conclusion can be drawn about the effectiveness of solvents based on their solubility levels for specific drugs?

Different drugs may require specific solvent combinations for optimal solubility Signup and view all the answers

What is the pH of a 0.5 M solution of sodium phenytoin given its pKa is 4.61?

9.15 Signup and view all the answers

For a buffer system consisting of 0.5 M acetic acid and 0.25 M sodium acetate, how would the pH compare to a buffer of higher concentrations?

It will have the same pH Signup and view all the answers

Given the pKb of trimethylamine is 4.2, what would be the expected pH of a 0.05 M trimethylamine solution?

9.8 Signup and view all the answers

What is the final pH of a buffer if NaOH is added resulting in a 0.02 unit increase in pH?

Increased by 0.02 units Signup and view all the answers

What is the definition of buffer capacity?

The ability to resist pH changes during dilution Signup and view all the answers

If acetic acid has a pKa of 4.76, how can the concentrations of acetic acid and acetate in a buffer at pH 4.5 be calculated?

Through the Henderson-Hasselbalch equation Signup and view all the answers

What is the resulting pH when mixing 0.05 M NaOH with a solution that has a pH of 6.0?

Increases slightly above 7.0 Signup and view all the answers

Which of the following statements about buffer solutions is NOT true?

The pH of a buffer depends entirely on its concentration Signup and view all the answers

What concentration of hydrogen ions corresponds to a pH of 4.5?

$3.16 imes 10^{-5}$ M Signup and view all the answers

In the presence of a strong base like NaOH, what effect does it have on a weak acid buffer solution?

It raises the pH slightly Signup and view all the answers

What defines a weak acid in terms of its ionization in solution?

It only partially ionizes in solution. Signup and view all the answers

What is the primary function of a buffer in a pharmaceutical formulation?

To maintain a stable pH. Signup and view all the answers

Which of the following accurately describes a saturated solution?

A solution that contains the maximum amount of solute at equilibrium. Signup and view all the answers

Which factor is most likely to decrease the solubility of a drug in solution?

Adding a foreign substance that interacts with the drug. Signup and view all the answers

When using the Henderson-Hasselbalch equation, what does an increase in pH typically indicate for a weak acid?

An increase in the fraction of the acid that is ionized. Signup and view all the answers

What is the self-preserving concentration of alcohol in pharmaceutical formulations?

40% by volume. Signup and view all the answers

What role do preservatives serve in pharmaceutical formulations?

To prevent microbial growth. Signup and view all the answers

In the context of liquid dosage forms, which vehicle is known for having mild osmotic laxative qualities?

Glycerin Signup and view all the answers

Which of the following statements about solubility is TRUE?

Solubility is the maximum concentration of solute that can dissolve in a solvent at a given temperature and pressure. Signup and view all the answers

What is a potential problem associated with excipients that act as osmotic laxatives in dosage forms?

They may lead to excessive fluid loss. Signup and view all the answers

Which of the following best defines a suspension in the context of liquid dosage forms?

A mixture where solid particles are dispersed in a liquid. Signup and view all the answers

What distinguishes medicated syrups from non-medicated syrups?

Medicated syrups include active pharmaceutical ingredients. Signup and view all the answers

What is one key disadvantage of using xylitol as a sweetener?

It may cause gastrointestinal upset in some individuals. Signup and view all the answers

Which term describes the process of separating active constituents from plant material through a solvent?

Percolation Signup and view all the answers

What are elixirs primarily characterized by?

Presence of alcohol and water. Signup and view all the answers

What defines a multi-phase system in liquid dosage forms?

A mixture of two immiscible liquids. Signup and view all the answers

What is a common characteristic of spirits in liquid preparations?

They are medicinal solutions of alcohol concentration greater than 10%. Signup and view all the answers

What is the main concern with the disulfiram (Antabuse) reaction related to certain excipients?

It can cause harmful interaction with alcohol. Signup and view all the answers

What distinct advantage do single-phase liquid dosage forms have compared to multi-phase formulations?

They maintain consistent drug concentration throughout. Signup and view all the answers

Study Notes

Chlordiazepoxide Solubility

Chlordiazepoxide solubility in water varies significantly with salt form.
For example:
- The base form has a solubility of 2.0 mg/mL H2O.
- The hydrochloride salt has a solubility of 0 to finite.

Acid-Base Theory (Brønsted-Lowry)

Weak acids have a finite Ka value.
The less dissociated a weak acid, the larger the [HA] concentration and the smaller the Ka value.

Weak Bases

Weak bases only partially dissociate in water.
They exist in solution in two forms:
- Uncharged, un-ionized species.
- Positively charged ions.

Typical Weakly Basic Functional Groups

Aliphatic amines.
Aromatic amines.
N-heterocycles including pyridine and imidazole.

Relationship between Ka and Kb

Ka x Kb = Kw = 10^-14.
pKW = -log10Kw = 14.
pKA = -log10KA.
pKB = -log10KB.
pKA + pKB = pKW = 14.

Practice Problem: Aspirin Un-ionization

Aspirin, a weak acid with a pKa of 3.5, is predominantly un-ionized in the stomach (pH = 1).
Approximately 99.7% of aspirin is un-ionized in the stomach.

pH and pKa Relationship

Weak acids are largely un-ionized when the pH is 2 units below their pKa.
Weak acids are largely ionized when the pH is 2 units above their pKa.
Weak bases are largely un-ionized when the pH is 2 units above their pKa.
Weak bases are largely ionized when the pH is 2 units below their pKa.

Drugs as Salts of Weak Acids and Bases

Salt forms of weak acids and bases may be preferred for pharmaceutical elegance.

Colorants

Artificial colorants in pharmaceuticals are regulated by the FDA.
Some patients may have allergies or sensitivities to artificial colorants.

Thickeners

Thickeners are viscosity-inducing agents and provide physical concealment of the drug.
Examples include celluloses (methylcellulose and sodium carboxymethylcellulose) and natural polymers (acacia and xanthan gum).

Solubilizing Agents

Surfactants can solubilize poorly water-soluble drugs.
Surfactants form micelles.
Examples include Tweens (polysorbates) and sodium oleate.

pH Adjusters

Acidifying agents provide an acidic medium for product stability.
Alkalinizing agents provide an alkaline medium for product stability.

Buffer Systems

Buffer systems resist changes in pH when small quantities of acid or base are added.
Examples include citric acid buffer, phosphoric acid buffer, and boric acid.

Tonicity Adjusters

Tonicity measures the effective osmotic pressure gradient.
Tonicity agents are used to render a solution similar in osmotic pressure to physiological fluids.
Examples include sodium chloride, dextrose, boric acid, and mannitol.

Single-Phase Liquid Systems

Solutions, syrups, elixirs, spirits, tinctures, aromatic waters, and fluid extracts are all single-phase liquid systems.
They are all variations of solutions, meaning that the drug is completely dissolved and evenly dispersed throughout the solvent.

Single-Phase Oral Systems

Advantages of single-phase oral systems include ease of swallowing, flexible dosing, and rapid onset of action.
Disadvantages include bulkiness, potential taste issues, drug instability in solution, and potential for inaccurate dosing.

Solutions

Solutions are liquid preparations that contain one or more drug substances dissolved in a suitable solvent.

Common Components of Elixirs

Active ingredient
Water
Alcohol
Sweeteners
Adjunct solvents (e.g., glycerin, propylene glycol)
Flavoring agents
Coloring agents
Preservatives

Elixirs: Preparation and Storage

Alcohol-soluble and water-soluble components are generally dissolved separately in alcohol and water, respectively.
The aqueous solution is added to the alcoholic solution.
Elixirs should be stored in tight, light-resistant containers protected from excessive heat.

Non-Medicated Elixirs

Non-medicated elixirs can be used for extemporaneous preparations, such as dilution of a medicated elixir.
The alcohol content of the non-medicated elixir should be similar to the medicated elixir being diluted.
Flavor and color should not conflict with the medicated elixir.

Weak Electrolytes

Only partially ionize in solution

Phosphate Ion

Acts as a Bronsted-Lowry base, accepting a proton to form HPO4-2

Acids and Bases

Acid: proton donor
Base: proton acceptor

Weak Base

Ammonia (NH3)

Sodium Phenytoin

Salt of a weak acid (phenytoin)

Strongest Base

A drug having a Kb of 1.74x10^-4

pH of Potassium Acetate

pH = 6.38

pH of Sodium Phenytoin

pH = 9.15

pH of Atropine Sulfate

pH = 10.6

pH of 0.05 M NaOH Solution

pH = 12.7

False Statements about Buffers

A buffer containing 0.05 M acetic acid and 0.05 M sodium acetate will have the same pH as one containing 0.5 M acetic acid and 0.5 M sodium acetate (pH depends upon the ratio of the components, not their concentration)

pH of Acetic Acid / Sodium Acetate Buffer

pH = 4.46

Buffer Capacity

0.83 M

Hydrogen Ion, Acetate Ion, and Acetic Acid Concentrations in a Buffer

[H+]= 3.16x10^-5 M
[Acetic acid] = 0.194 M
[Acetate] = 0.106 M

Taste of Free Base

Bitter

Co-Solvent Advantages

Increase solubility of poorly soluble drugs
Enhance stability of drug solutions

Flavoring Aliquot

Use 29.4 mL dilution, with 4.2 mL aliquot containing 0.6 mL flavoring

Peppermint Oil Aliquot

Use 45 mL dilution, with 3 mL aliquot containing 0.2 mL peppermint oil

Exothermic Drug

Releases heat when dissolving

Solvents

Alcohol, USP has a lower dielectric constant than water
Fixed oils are not water-miscible
Glycerin is often used as a humectant within otic solutions

Taste Bud Anesthesia

Local anesthetics can mask taste by anesthetizing the taste buds

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Description

Test your knowledge on acid-base theory, focusing on weak acids and bases, their solubility in different forms, and the key relationships between pKa and pKb. This quiz includes practice problems to apply these concepts effectively.