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Questions and Answers
How is a percent solution defined in terms of components by weight?
How is a percent solution defined in terms of components by weight?
- Parts per 100 of solution (correct)
- Parts per 10 of solution
- Parts per 50 of solution
- Parts per 1000 of solution
If making a 5% (w/w) aqueous solution of hydrochloric acid, what principle is being used?
If making a 5% (w/w) aqueous solution of hydrochloric acid, what principle is being used?
- The volume must always be adjusted up to 100 mL
- The total amount must be multiplied by the percentage (correct)
- Only the weight of the solute matters
- Molecular weight weight is irrelevant
What volume of HCl is needed to prepare 50 mL of a 2% (v/v) solution?
What volume of HCl is needed to prepare 50 mL of a 2% (v/v) solution?
- 2 mL of HCl (correct)
- 100 mL of HCl
- 50 mL of HCl
- 1 mL of HCl
When preparing a percent solution, which of the following is necessary to ensure accuracy?
When preparing a percent solution, which of the following is necessary to ensure accuracy?
What is the effect of molecular weight when expressing percent solutions?
What is the effect of molecular weight when expressing percent solutions?
What happens when the ratio of [A−] to [HA] is equal to 1?
What happens when the ratio of [A−] to [HA] is equal to 1?
What is the term used to describe the dissociation constant of a weak acid?
What is the term used to describe the dissociation constant of a weak acid?
Which factor influences the buffering capacity of a solution?
Which factor influences the buffering capacity of a solution?
What effect does increasing ionic strength have in a buffer solution?
What effect does increasing ionic strength have in a buffer solution?
What will occur if the dissociation constant Ka of a weak acid is very small?
What will occur if the dissociation constant Ka of a weak acid is very small?
In buffer solutions, how is the conjugate base often referenced?
In buffer solutions, how is the conjugate base often referenced?
Which equation can be used to calculate the dissociation constant Ka of a weak acid?
Which equation can be used to calculate the dissociation constant Ka of a weak acid?
What condition is necessary for a weak acid to achieve maximum buffering capacity?
What condition is necessary for a weak acid to achieve maximum buffering capacity?
What is the primary purpose of TC devices in laboratory settings?
What is the primary purpose of TC devices in laboratory settings?
How is a temperature in Celsius converted to Fahrenheit?
How is a temperature in Celsius converted to Fahrenheit?
What type of glass is commonly used for disposable materials in laboratories?
What type of glass is commonly used for disposable materials in laboratories?
Which of the following statements about temperature-dependent reactions is correct?
Which of the following statements about temperature-dependent reactions is correct?
Which glassware category is specifically known for its resistance to acid and alkali?
Which glassware category is specifically known for its resistance to acid and alkali?
What characterizes plasticware compared to traditional glassware in laboratory settings?
What characterizes plasticware compared to traditional glassware in laboratory settings?
Which type of glassware should ideally be used for enzyme determinations requiring precise temperature control?
Which type of glassware should ideally be used for enzyme determinations requiring precise temperature control?
What is a common use of a heating/cooling cell in laboratory practices?
What is a common use of a heating/cooling cell in laboratory practices?
What is a primary advantage of using automatic pipettes?
What is a primary advantage of using automatic pipettes?
Which type of pipette is described as being able to select different volumes?
Which type of pipette is described as being able to select different volumes?
What is a characteristic of micropipettes?
What is a characteristic of micropipettes?
In what situation should disposable transfer pipettes be used?
In what situation should disposable transfer pipettes be used?
What does the term 'automatic' imply when referring to automatic pipettes?
What does the term 'automatic' imply when referring to automatic pipettes?
What defines a fixed volume pipette?
What defines a fixed volume pipette?
What type of pipette can dispense fluid to multiple wells at once?
What type of pipette can dispense fluid to multiple wells at once?
What defines an automatic macropipette?
What defines an automatic macropipette?
How should you properly prepare a solution when adding acid to water?
How should you properly prepare a solution when adding acid to water?
What is the definition of molarity (M)?
What is the definition of molarity (M)?
What is a common method for calculating the amount of substance needed for a percent solution?
What is a common method for calculating the amount of substance needed for a percent solution?
What amount of concentrated HCl is needed to make the solution as described?
What amount of concentrated HCl is needed to make the solution as described?
What is the meaning of the term 10% (w/v) solution?
What is the meaning of the term 10% (w/v) solution?
Which solution is a 5% aqueous solution typically calculated from?
Which solution is a 5% aqueous solution typically calculated from?
What should be done after mixing concentrated HCl with water according to the preparation instructions?
What should be done after mixing concentrated HCl with water according to the preparation instructions?
What is the equivalent of 1 mol of a substance in terms of grams?
What is the equivalent of 1 mol of a substance in terms of grams?
Study Notes
Vessel Designations
- TC (Contain) vessels do not deliver measured volume; TD (Deliver) vessels dispense the specified amount.
- Accuracy in delivering liquid is crucial for laboratory processes, especially during transfers.
Temperature Conversion
- Convert Celsius to Fahrenheit using the formula: °F = (°C × 9/5) + 32.
- Convert Fahrenheit to Celsius with: °C = (°F - 32) × 5/9.
Types of Laboratory Glassware
- Common glass types:
- Kimax/Pyrex (borosilicate)
- Corex (aluminosilicate)
- High silica glass
- Vycor (acid/alkali resistant)
- Low actinic (amber colored)
- Flint (soda lime glass)
- Clinical chemistry glassware should be high thermal resistance, such as borosilicate or aluminosilicate.
Temperature Control in Reactions
- Optimal temperature is critical for analytic reactions, especially enzyme determinations.
- Various methods exist for heating or cooling samples, such as heating blocks or water baths.
Automatic Pipettes
- Types include fixed volume, variable volume, and multichannel variants.
- Automatic pipettes enhance safety, stability, and ease of use, reducing the necessity for cleaning due to disposable tips.
- Micropipettes handle less than 1 mL; macropipettes manage over 1 mL volumes.
- Multichannel pipettes can dispense fluid to multiple wells simultaneously, improving efficiency in techniques like assay processes.
Weak Acids and Buffers
- Weak acids have minimal dissociation compared to strong acids; described using the Henderson-Hasselbalch equation.
- The equation includes dissociation constant (Ka) for weak acids, also expressed as pKa.
- Buffer capacity is greatest when the concentration ratio of conjugate base ([A−]) to weak acid ([HA]) is 1.
Ionic Strength and Buffers
- Ionic strength influences buffer behavior, particularly in analytical separation techniques.
- Higher ionic strength decreases particle migration rates, affecting separation efficiency.
Preparing Percent Solutions
- Percent solutions denote concentration as "parts per 100" (e.g., % w/v).
- Weight/volume (% w/v), volume/volume (% v/v), and weight/weight (% w/w) are methods to express concentrations.
- Example procedure for a weight/volume (w/v) solution:
- To create a 10% NaOH solution: Determine grams of NaOH needed for 1000 mL of solution.
Calculation Approaches
- Percent solutions can be calculated using either direct fraction multiplication or ratios, depending on the desired final volume.
- Always add acid to water when diluting to ensure safety.
Molarity
- Molarity expresses concentration as moles per liter (mol/L) or millimoles per milliliter (mmol/mL).
- Conversion from weight to molarity requires understanding molar mass and existing concentration units during preparation.
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Description
Test your knowledge on the functionalities of vessels designed for containing or delivering liquids. This quiz also includes a section on converting temperatures from Celsius to Fahrenheit, integrating practical applications in fluid mechanics.
