Podcast
Questions and Answers
What is the primary purpose of diluting a standard solution?
What is the primary purpose of diluting a standard solution?
Which formula is used to determine the relationship between concentrations and volumes during dilution?
Which formula is used to determine the relationship between concentrations and volumes during dilution?
When transferring a specific volume of solution, which equipment would be considered the most precise?
When transferring a specific volume of solution, which equipment would be considered the most precise?
In a serial dilution, what happens to the concentration of the solution at each step?
In a serial dilution, what happens to the concentration of the solution at each step?
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What volume of deionized water should be added to a 10.0 cm3 aliquot to achieve a total volume of 100 cm3?
What volume of deionized water should be added to a 10.0 cm3 aliquot to achieve a total volume of 100 cm3?
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What defines a concentrated solution?
What defines a concentrated solution?
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Which of these correctly describes molar concentration?
Which of these correctly describes molar concentration?
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What is the primary component of a solution?
What is the primary component of a solution?
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Which statement about aqueous solutions is accurate?
Which statement about aqueous solutions is accurate?
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What term is used for stock solutions with a known concentration?
What term is used for stock solutions with a known concentration?
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When calculating mass concentration of a solution, what is the correct formula?
When calculating mass concentration of a solution, what is the correct formula?
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Which statement best describes a dilute solution?
Which statement best describes a dilute solution?
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What unit is most commonly used for molar concentration?
What unit is most commonly used for molar concentration?
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Study Notes
Solutions
- Solutions are homogeneous mixtures of two or more components
- Each solution is made up of a solvent and one or more solutes
- The solvent is usually the major component
- The properties of the solution are similar to the properties of the solvent
- Aqueous solutions have water as the solvent
Solutions and Concentration
- A concentrated solution has a high proportion of solute and a high ratio of solute to solvent
- Concentrated solutions generally have more than 10 g of solute per 100 g of solvent
- A dilute solution has a small proportion of solute and a low ratio of solute to solvent
Which solution has most particles?
- Visual analysis of diagrams (A, B, and C) is needed to determine which solution (A, B, or C) has the most particles per cm³.
Practice Calculation
- Mass concentration of a solution is calculated by dividing the mass of the solute by the volume of the solvent.
- Example: 4.5 g NaOH in 500 cm³ solution = 0.009 g cm⁻³
Molar Concentration (Molarity)
- Molar concentration (or molarity) is the number of moles of solute per cubic decimeter (dm³) of the solution
- Formula: csolute = nsolute / Vsolution
- The most common unit of molar concentration is mol dm⁻³
- Molarity is also represented as mol/L or M
What is a Standard Solution?
- Standard solutions are stock solutions with a known concentration of solute
Technique: Making a Standard Solution
- The process involves steps like adding a solid solute, adding solvent and/or transferring a solution into another container
Naming Equipment
- Diagrams (a) to (f) show different pieces of laboratory equipment (e.g., beakers, volumetric flasks, measuring cylinders, pipettes)
- Students need to identify what each laboratory equipment is.
Practice Question (Potassium Hydrogen Phthalate)
- A 280.0 cm³ standard solution of potassium hydrogen phthalate (KHP) was prepared via dissolving 0.430 g in distilled water.
- Calculate the concentration in mol dm⁻³
- Outline how a 10-fold dilution to make 100 cm³ is performed.
- Identify two pieces of precise equipment needed for dilution.
Dilution
- Dilution is the process of making a solution less concentrated
- Dilution formula: C₁V₁ = C₂V₂ (where C₁ is initial concentration, V₁ is initial volume, C₂ is final concentration, and V₂ is final volume.)
- Chemicals are often stored as concentrated stock solutions, and diluted as needed.
Example Calculation
- Examples provided on how to calculate concentrations of standard solutions using different volumes and masses
- The examples often include dissolving substances (like sodium carbonate) in volumetric flasks and measurements of volumes with varying equipment like volumetric flasks and pipettes.
Serial Dilutions
- A serial dilution is a series of dilutions where the concentration decreases by a set amount at each step
- Common technique (e.g. ultraviolet spectroscopy)
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Description
Test your knowledge on the properties of solutions, including definitions of concentrated and dilute solutions. This quiz also covers how to calculate mass concentration and compares different solutions based on particle count. Perfect for chemistry students looking to reinforce their understanding of solutions.
