Questions and Answers
What is the standard temperature for measuring specific gravity in the US Pharmacopeia?
Which statement best describes specific gravity?
How is the specific gravity of an unknown liquid calculated using a pycnometer?
According to Archimedes' principle, what does the upward buoyant force on a body immersed in a fluid equal?
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In calculating specific gravity, why is it important to account for differences in temperature for different substances?
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What is the definition of density in the context of pharmaceuticals?
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Which of the following statements about drug stability is true?
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What factor significantly influences the bioavailability of a drug?
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Which method is NOT classified as a drug delivery system?
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How are gases typically characterized in terms of density compared to solids?
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What does dissolution refer to in the context of drug delivery?
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Which of the following best describes bioavailability?
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What is the correct relationship among mass, volume, and density?
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What determines the weights of components in an admixture solution?
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Which of the following statements is true regarding molarity?
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What is the primary focus of bioavailability factors in pharmaceutical sciences?
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In the context of drug stability, which factor is least likely to affect a drug's shelf life?
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Which concentration expression involves weight of solute relative to the volume of solution?
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What is primarily calculated using molecular weight from grams?
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How is molality defined in terms of concentration?
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In drug delivery systems, which aspect does not typically influence absorption?
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Which formula expresses the % volume in volume concentration?
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How do you calculate the specific gravity of a solid that is heavier than and insoluble in water?
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What is the specific gravity of a substance that weighs 50 g in air and displaces 20 g of water?
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If a solid weighs 15 g in air and 10 g when submerged in a liquid with a specific gravity of 0.9, what is the specific gravity of the solid?
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Which of the following is the correct formula for calculating the specific gravity of a substance when given its weight in air and its weight in liquid?
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What is the specific gravity of a crystal that weighs 6.423 g in air and 2.873 g in an oil with a specific gravity of 0.858?
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In which situation would specific gravity be particularly important in a pharmaceutical context?
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How does specific gravity help in total parenteral nutrition (TPN) admixtures?
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What happens to the specific gravity of a substance if it is placed in a liquid that has a higher specific gravity than itself?
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If a piece of glass weighs 38.525 g in air and 23.525 g in water, what is the weight of the water displaced?
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Which of the following substances is heavier than water and soluble in it?
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Molarity is a concentration expression based solely on the mass of solute in a specific volume of solution.
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Normality is one of the concentration expressions used only for acids and bases in pharmaceutical applications.
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The formula for % weight in volume concentration considers both the weight of solute and the total volume of the solution.
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Volume of solution is irrelevant when calculating concentration units.
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Molecular weight is used to convert grams into moles for concentration calculations.
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Density is defined as the measure of volume per unit of mass.
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Drug stability refers to a drug's ability to maintain its properties over time and under varying conditions.
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All liquids and solids have the same density at a temperature of 20 degrees Celsius.
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The solubility of a drug is the amount of drug that can dissolve in a given solvent at a specified temperature.
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Transdermal systems are types of drug delivery systems that do not optimize drug administration.
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Physical pharmacy studies how drugs interact with their environment, influencing their efficacy.
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Higher temperatures generally lead to lower solubility for most solid drugs in solvents.
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Solids generally have higher densities compared to gases.
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Specific gravity is defined as the ratio of a substance's density to the density of a standard substance.
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The standard temperature for measuring specific gravity in the US Pharmacopeia is 20 °C.
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Using a pycnometer, the specific gravity of a liquid can be calculated by dividing the weight of the liquid by the weight of an equal volume of water.
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Archimedes' principle states that the weight of a body immersed in a fluid is equal to the weight of the fluid that it displaces.
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The specific gravity of a liquid is expressed in units, making it easier to compare with other substances.
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A heavier liquid will always sink below a lighter liquid when layered in a test tube.
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Different substances expand or contract at the same rate with temperature changes, making specific gravity calculations less important.
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To determine the specific gravity of a plummet, its weight in air must be compared to its weight in the water it displaces.
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Mineral oil has a higher specific gravity than water.
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It is unnecessary to use a pycnometer for calculating the specific gravity of liquids.
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The specific gravity of a solid that is heavier than and soluble in water can be found by dividing the weight of the solid in air by the weight of water it displaces.
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To calculate the specific gravity of a substance, both its weight in air and weight in a liquid must be measured.
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Specific gravity is less important in pharmaceutical applications compared to other scientific fields.
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If a glass plummet weighs 12.64 g in air and 9.12 g in oil, the weight of the displaced oil can be directly used to calculate its specific gravity.
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The apparent loss of weight of a solid in liquid is equal to the weight of the liquid displaced.
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The specific gravity of oil is high if it is less dense than water.
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A specific gravity less than 1 indicates that an object will sink in a fluid.
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In calculating specific gravity, a pharmacist can use any liquid of known specific gravity when the solid is insoluble in water.
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The specific gravity of glass, calculated from its weight in air and water, is higher than 2.
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If the weight of a solid in water is greater than the weight in air, the specific gravity would be less than 1.
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Study Notes
Introduction to Physical Pharmacy
- Physical Pharmacy studies the physical and chemical properties of drugs and drug delivery systems.
- Focuses on drug interactions with the environment, impacting efficacy, safety, and stability.
- Aims to develop drug delivery systems for optimized patient outcomes.
Key Areas of Focus
-
Drug Solubility and Dissolution:
- Solubility indicates the quantity of drug that dissolves in a solvent at a specific temperature.
- Dissolution is the process where a solid drug dissolves in a solvent, crucial for bioavailability.
-
Drug Stability:
- Refers to a drug's ability to retain its properties over time and varying conditions.
Drug Delivery Systems
- Classified into:
- Oral
- Transdermal
- Inhalation
- Parenteral
Density and Specific Gravity
-
Density:
- Defined as mass per unit of volume; varies with pressure and temperature.
- Example: 100 g of water occupies 100 mL at 20°C, demonstrating a 1:1 relationship.
-
Specific Gravity:
- Ratio of density of a substance to the density of a standard (typically water).
- Expressed as weight of the substance divided by the weight of an equal volume of water; no unit, numerically equivalent to density.
Concentration Expressions
- Concentration measures the amount of solute in a solution, essential in pharmaceutical applications.
- Common concentration units include:
- Molarity: Moles of solute per liter of solution.
- Molality: Moles of solute per kilogram of solvent.
- Normality: Equivalents of solute per liter of solution.
- Percent weight/volume: Grams of solute per 100 mL of solution.
Calculating Moles
- Moles can be calculated using the equation: Moles = grams / molecular weight.
Pharmaceutical Applications of Specific Gravity
- Used for converting weight to volume in formulations.
- Important for calculating strengths of ingredients based on weight or volume.
- Essential in preparing parenteral nutrition admixtures.
Methods of Determining Specific Gravity
-
Using a Pycnometer:
- Measure the weight of the pycnometer filled with water and an unknown liquid; calculate specific gravity accordingly.
-
Displacement Method:
- Based on Archimedes' principle, which states that the buoyant force equals the weight of the displaced fluid.
- Specific gravity determined by measuring weights in air, water, and the solution of interest.
Example Calculations
- For a plummet weighing 12.64 g in air, 8.57 g in water, and 9.12 g in oil, specific gravity of oil calculated from the weights of displaced fluid.
- A solid weighing 38.525 g in air and 23.525 g in water yields a specific gravity of 2.568 by measuring the weight of displaced water.
- For a chemical salt weighing 6.423 g in air and 2.873 g in oil, knowing the oil's specific gravity allows calculation of the salt's specific gravity as 1.55.
Important Notes
- Accurate measurement of specific gravities must account for temperature variations, as substances expand or contract differently.
- Standard temperature for specific gravity in pharmaceuticals is typically at 25°C, with exceptions for alcohol at 15.56°C.
Introduction to Physical Pharmacy
- Physical pharmacy studies the physical and chemical properties of drugs and their delivery systems.
- It examines drug interactions with their environment, including effects on efficacy, safety, and stability.
- Key focus areas include drug solubility, dissolution, and stability.
Drug Solubility and Dissolution
- Solubility: amount of drug dissolving in a solvent at a specific temperature.
- Dissolution: the process of a solid drug dissolving in a solvent.
- Both are critical factors influencing bioavailability.
Drug Stability
- Stability refers to a drug's ability to maintain physical, chemical, and biological properties over time and under various conditions.
Drug Delivery Systems
- Delivery systems optimize the administration of drugs and improve patient outcomes.
- Types include oral, transdermal, inhalation, and parenteral systems.
Density and Specific Gravity
- Density: mass per unit volume; varies with pressure and temperature.
- Example: Water's density is 1 g/mL at 20°C, but this varies by substance.
- Specific gravity is the ratio of a substance's density to that of a reference (usually water).
Measuring Specific Gravity
- Specific gravity does not have units and is numerically equal to density.
- Calculated using the formula: Specific gravity = weight of substance / weight of equal volume of water.
- Common standard temperature for specific gravity is 25°C, except for alcohol at 15.56°C.
Archimedes' Principle
- The principle states that the upward buoyant force on an immersed body equals the weight of the fluid displaced.
- This is fundamental in fluid mechanics for determining specific gravity and densities.
Practical Applications of Specific Gravity
- Used in calculating weights of pharmaceutical ingredients based on volume.
- Essential in preparing total parenteral nutrition (TPN) admixtures utilizing specific gravity for component weights.
Concentration Expressions
- Concentrations in pharmaceutical sciences refer to solutions with solute and solvent.
- Different expressions are utilized based on application needs, including molarity, molality, and normality.
Molarity and Other Concentration Units
- Molarity: moles of solute per liter of solution.
- Other expression formulas include % weight/volume, % volume/volume, and % weight/weight.
- Different concentration expressions serve various pharmaceutical calculations and applications.
Preparation for Assessment
- Understanding these concepts is vital for success in modular quizzes in physical pharmacy.
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Description
Explore the foundational concepts of Physical Pharmacy in this module. Learn about the physical and chemical properties of drugs, their interactions with the environment, and how these factors impact drug efficacy and safety. A crucial study for anyone interested in pharmaceutical sciences.
