Chapter 7: Before Equivalence Point | CHM 214 | 067

Jacob Stewart
11 Feb 202105:12
EducationalLearning
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TLDRThe video script discusses a chemical reaction involving a silver solution and a chloride solution. It explains the process of calculating the concentration of silver in the solution after adding 10 milliliters of the silver solution to 25 milliliters of the chloride solution at a concentration of 0.1 molar. The script details the conversion of volumes to moles, the reaction of silver with chloride to form silver chloride, and the use of the solubility product (Ksp) to determine the final concentration of silver ions remaining in the solution. The result indicates a very low concentration of silver ions, which is expressed as a p value for clarity.

Takeaways
  • 🧪 The problem involves calculating the concentration of silver in a solution after adding 10 milliliters of silver solution.
  • 📝 The initial step is to convert the volume of silver solution (10 mL) into moles of silver.
  • 🧬 The concentration of the silver solution is given as 0.05 molar, which is used to find the moles of silver.
  • 📊 By multiplying the volume (10 mL) by the concentration (0.05 molar), 0.5 millimoles of silver are determined to be added.
  • 🧫 The chloride concentration in the solution is 0.1 molar with a volume of 25 mL, resulting in 2.5 millimoles of chloride.
  • 🌐 The reaction is not at equilibrium; all the added silver is expected to react with the chloride.
  • ⚗️ After the reaction, 2.0 millimoles of chloride are assumed to be left, considering the complete reaction of silver.
  • 🔍 The solubility product (Ksp) is used to find the concentration of silver ions remaining in the solution after the precipitation of silver chloride.
  • 📈 Ksp is calculated as the concentration of silver times the concentration of chloride, with the known values being used to find the concentration of silver.
  • 📉 The concentration of silver is found to be very low (3.15 x 10^-9 molar), indicating that it is likely difficult to detect.
  • 📌 The final result is often expressed as the p value (pAg), which is the negative logarithm (base 10) of the silver concentration, resulting in a pAg of 8.50.
Q & A

  • What is the initial concentration of the silver solution?

    -The initial concentration of the silver solution is 0.05 molar.

  • How many millimoles of silver are present in the 10 milliliters of silver solution?

    -There are 0.5 millimoles of silver in the 10 milliliters of silver solution, calculated by multiplying the volume (10 mL) by the concentration (0.05 molar).

  • What is the initial concentration of chloride in the solution?

    -The initial concentration of chloride is 0.1 molar.

  • How many millimoles of chloride were originally present in the 25 milliliters of chloride solution?

    -There were 2.5 millimoles of chloride initially, calculated by multiplying the volume (25 mL) by the concentration (0.1 molar).

  • What happens to the chloride when silver is added to the solution?

    -When silver is added to the solution, it reacts with the chloride to form silver chloride, reducing the amount of chloride to 2.0 millimoles.

  • What is the solubility product (Ksp) for silver chloride mentioned in the script?

    -The solubility product (Ksp) for silver chloride is 1.8 × 10^-10.

  • How can the concentration of silver ions remaining in solution after the reaction be determined?

    -The concentration of silver ions can be determined using the Ksp value. It is calculated by dividing the Ksp by the concentration of chloride remaining in the solution.

  • What is the calculated concentration of silver ions in solution after the reaction?

    -The calculated concentration of silver ions in solution is approximately 0.057 molar.

  • How can the concentration of silver ions be expressed in terms of pAg?

    -The concentration of silver ions can be expressed as pAg, which is the negative logarithm (base 10) of the silver ion concentration. For the given concentration of 3.15 × 10^-9 molar, pAg is 8.50.

  • What is the significance of pAg in this context?

    -pAg represents the acidity or basicity of the solution in terms of silver ion concentration. A lower pAg value indicates a higher concentration of silver ions in the solution.

  • How does the equivalence point relate to the scenario described in the script?

    -The equivalence point is the point at which the amount of silver added would have completely reacted with the chloride to form silver chloride. Before the equivalence point, as described in the script, there is excess chloride and some unreacted silver ions remain in the solution.

  • What will be the focus of the next video mentioned in the script?

    -The next video will focus on the scenario when the solution is at the equivalence point, which is when all the chloride has reacted with the silver to form silver chloride and no unreacted chloride or silver remains.

Outlines
00:00
🧪 Calculation of Silver Concentration in a Reaction

This paragraph discusses the process of calculating the concentration of silver in a chemical reaction. It begins by setting up the problem, stating that 10 milliliters of silver solution is added to a solution and the task is to find the concentration of silver. The speaker explains the need to convert the volume of silver to moles and uses the given concentration rate of 0.05 molar to determine the moles of silver added. The paragraph then addresses the chloride present, which is 25 milliliters at a concentration of 0.1 molar, and calculates the moles of chloride. The main focus is on the reaction between silver and chloride, where all added silver is assumed to react, leaving 2.0 millimoles of chloride. The concept of solubility product (Ksp) is introduced to find the concentration of silver ions remaining in the solution after the precipitation reaction. The calculation involves dividing the Ksp value by the concentration of chloride and adjusting for the total volume of the solution. The final concentration of silver is found to be very low, indicated by a negative log base 10 value of 8.50.

05:01
📈 Strategy for Analyzing Volumes Before Equivalence Point

The second paragraph outlines a strategy for dealing with volumes before the equivalence point in a titration. It emphasizes that the same approach used in the first paragraph can be applied to any volume, not just the one discussed. The speaker mentions that the next video will focus on the equivalence point, suggesting a continuation of the topic in subsequent content. This paragraph serves as a bridge, connecting the current discussion on silver concentration to future discussions on the equivalence point in titration analysis.

Mindmap
Keywords
💡Concentration
Concentration refers to the amount of a particular substance (solute) present in a given quantity of solution (solvent). In the context of the video, it is used to determine the moles of silver in the solution, which is calculated based on the volume and molarity of the silver solution. This concept is crucial as it helps in understanding the chemical reactions and the formation of precipitates like silver chloride.
💡Moles
Moles are a fundamental concept in chemistry that represent the amount of substance. It is used to quantify the number of atoms, ions, or molecules in a sample. In the video, moles of silver are calculated from the volume and concentration of the silver solution to understand the chemical reaction that occurs upon its addition to the chloride solution.
💡Silver Solution
Silver solution is a chemical mixture containing silver ions in a solvent, often used in educational demonstrations and chemical reactions, such as precipitation reactions with chloride ions. In the video, the silver solution is added to a chloride solution to illustrate the formation of silver chloride precipitate.
💡Chloride Solution
Chloride solution contains chloride ions and is used in chemical reactions, particularly in precipitation reactions with metal ions like silver. The video focuses on the reaction between silver and chloride ions to form silver chloride precipitate, a key concept in understanding the reaction dynamics.
💡Precipitation Reaction
A precipitation reaction occurs when two soluble substances in solution react to form an insoluble compound, which then precipitates out of the solution. In the video, the reaction between silver ions and chloride ions results in the formation of silver chloride precipitate, illustrating the concept of precipitation.
💡Solubility Product (Ksp)
The solubility product, denoted as Ksp, is a measure of the maximum amount of a substance that can dissolve in a solution at a given temperature. It is used to predict whether a precipitate will form and to calculate the concentrations of ions in a saturated solution. In the video, Ksp is used to determine the concentration of silver ions remaining in solution after the precipitation reaction.
💡Equivalence Point
The equivalence point in a titration is the point at which the amount of titrant added is stoichiometrically equivalent to the amount of analyte present. It indicates the point at which the reaction is complete. The video mentions that the discussion will focus on the situation before the equivalence point, where all the silver reacts with the chloride.
💡Silver Chloride (AgCl)
Silver chloride (AgCl) is a white, insoluble salt that forms as a precipitate in the reaction between silver ions and chloride ions. It is used in various applications, including as a catalyst and in the production of some types of mirrors. In the video, the formation of AgCl precipitate is a key visual and educational element of the chemical reaction being discussed.
💡Significant Figures
Significant figures are the digits in a number that carry meaning contributing to its precision. This includes all digits except leading zeros. In scientific calculations, retaining the correct number of significant figures is important for accuracy and clarity. The video emphasizes the importance of significant figures when calculating and reporting the concentration of silver ions in the solution.
💡pAg
pAg is the negative logarithm (base 10) of the silver ion concentration. It is used in analytical chemistry to express the activity or concentration of silver ions in a solution, particularly in relation to the solubility of silver compounds. The video uses pAg to express the very low concentration of silver ions remaining in solution after the precipitation reaction.
💡Molarity
Molarity is a measure of the concentration of a solution and is defined as the number of moles of solute per liter of solution. It is a key concept in chemistry for understanding and performing dilutions, calculations, and reactions. In the video, molarity is used to convert millimoles to a concentration that can be compared with the solubility product constant.
Highlights

The problem involves calculating the concentration of silver in a solution after adding 10 milliliters of silver solution.

The initial step is to convert the 10 milliliters of silver into moles of silver.

The concentration of the silver solution is given as 0.05 molar, which is used to determine the moles of silver.

The calculation is simplified by expressing the concentration in terms of millimoles per milliliter.

There are 0.5 millimoles of silver added to the solution based on the given concentration rate.

The initial amount of chloride present is 25 milliliters at a concentration of 0.1 molar.

The total moles of chloride is calculated to be 2.5 millimoles.

The reaction between silver and chloride is assumed to be complete, with all silver reacting.

Despite complete reaction, a small amount of silver chloride solid forms due to the precipitation reaction.

The solubility product (Ksp) is used to find the concentration of silver ions remaining in the solution after the reaction.

The Ksp value for the silver chloride reaction is given as 1.8 times 10 to the power of negative 10.

The concentration of chloride after the reaction is 2.0 millimoles, derived from the initial amount subtracted by the reacted silver.

The concentration of silver is found by dividing the Ksp value by the concentration of chloride.

The calculation results in a silver concentration of approximately 0.057 molar.

The final concentration of silver is expressed as 3.15 times 10 to the power of negative 9 molar, considering significant figures.

The p value, which is the negative log base 10 of the silver concentration, is calculated to be 8.50.

The strategy outlined can be applied to find the concentration of silver for any volume, not just at the equivalence point.

Transcripts

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Chemistry ExperimentSilver SolutionChloride ReactionSolubility ProductPrecipitation AnalysisMolarity CalculationEquivalence PointChemical ReactionsLab TechniquesAnalytical Chemistry