Chapter 7: At Equivalence Point | CHM 214 | 068

Jacob Stewart
11 Feb 202103:46
EducationalLearning
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TLDRThe video script discusses the concept of the equivalence point in titration, using a specific example where 2.5 millimoles of chloride react with silver in a 1:1 stoichiometry to form silver chloride. It explains that at the equivalence point, the concentration of silver equals the concentration of chloride, which can be calculated using the solubility product constant (Ksp). The script provides a step-by-step calculation, showing that the concentration of silver at the equivalence point is significantly higher than before, with a corresponding decrease in the p-value, indicating a substantial change in silver concentration.

Takeaways
  • 📈 The equivalence point in titration is reached when 2.5 millimoles of chloride react with an equal amount of silver.
  • 🧪 The volume at the equivalence point is determined to be 50 milliliters using the known concentration of silver at 0.05 millimoles per milliliter.
  • 🌟 At the equivalence point, the concentration of silver is equal to the concentration of chloride due to the one-to-one stoichiometry of the reaction.
  • 💡 The solubility product (ksp) concept is introduced to explain the concentration of silver and chloride at the equivalence point, considering the formation of the salt and its solubility.
  • 📊 The concentration of silver and chloride at equilibrium can be found by treating it as an equilibrium problem and using the ksp value.
  • 🔢 The ksp value for silver chloride is given as 1.8 times 10 to the minus 10, which is used to calculate the concentration of silver at the equivalence point.
  • 📈 The concentration of silver increases dramatically from 10 to the negative 9 in the previous video to 1.34 times 10 to the minus 5 at the equivalence point.
  • 📉 The p-value changes significantly from 8.5 to 4.87 at the equivalence point, indicating a higher concentration of silver.
  • 🔄 The concept of some of the salt redissolving in a very small amount and being governed by ksp is introduced to explain the final concentrations.
  • 📝 The process of solving for the concentration of silver at the equivalence point involves setting up an equation based on ksp and solving for x, which represents the concentration of both silver and chloride.
  • 🔍 The equivalence point serves as a critical point in the titration curve and understanding its significance is essential for accurately determining the concentration of substances in a solution.
Q & A

  • What is the equivalence point in titration?

    -The equivalence point in titration is the volume at which the reactants in a titration reaction are stoichiometrically equivalent, meaning they have reacted with each other in a one-to-one ratio.

  • How many millimoles of chloride were calculated in the previous video?

    -In the previous video, 2.5 millimoles of chloride were calculated.

  • What is the stoichiometry of the reaction between silver and chloride?

    -The stoichiometry of the reaction between silver and chloride is one-to-one, meaning one mole of silver reacts with one mole of chloride to form silver chloride salt.

  • What is the concentration of silver used in the titration?

    -The concentration of silver used in the titration is 0.05 millimoles per milliliter.

  • What is the volume at the equivalence point for this titration?

    -The volume at the equivalence point for this titration is 50 milliliters.

  • How is the concentration of silver at the equivalence point determined?

    -The concentration of silver at the equivalence point is determined by considering the solubility product (ksp). Since all the chloride has reacted to form the salt, the concentration of silver and chloride in the solution will be governed by ksp.

  • What does ksp represent in the context of this titration?

    -In the context of this titration, ksp represents the solubility product constant, which is a measure of the solubility of the silver chloride salt formed. It is the product of the concentrations of silver and chloride ions at equilibrium.

  • What is the value of ksp for silver chloride?

    -The value of ksp for silver chloride is 1.8 times 10 to the minus 10.

  • How can we calculate the concentration of silver at the equivalence point?

    -We can calculate the concentration of silver at the equivalence point by setting up the equation ksp = [Ag+][Cl-] and solving for the concentration of silver (x), since [Ag+] = [Cl-] at the equivalence point. Taking the square root of ksp gives us the concentration of silver.

  • What is the calculated concentration of silver at the equivalence point?

    -The calculated concentration of silver at the equivalence point is 1.34 times 10 to the minus 5 molar.

  • How does the concentration of silver change from the previous video to the equivalence point?

    -The concentration of silver changes dramatically from the previous video to the equivalence point, increasing from 10 to the negative 9 molar to 1.34 times 10 to the minus 5 molar, which is several orders of magnitude higher.

  • What is the p-value of silver at the equivalence point?

    -The p-value of silver at the equivalence point is 4.87. It is important to note that a lower p-value indicates a higher concentration.

  • How does the p-value change from the previous video to the equivalence point?

    -The p-value changes from 8.5 in the previous video to 4.8 at the equivalence point, indicating a significant increase in the concentration of silver.

Outlines
00:00
📈 Equivalence Point Calculation and Silver Concentration

This paragraph discusses the concept of the equivalence point in titration, where the volume at the equivalence point is determined based on a 1:1 stoichiometry between silver and chloride. The calculation involves using the previously determined 2.5 millimoles of chloride and the concentration of silver, which is 0.05 millimoles per milliliter, to find that the equivalence point occurs at 50 milliliters. The paragraph further explains that at the equivalence point, the concentration of silver equals the concentration of chloride due to the complete reaction to form the salt. However, a small amount of the salt remains soluble, and its solubility is governed by the solubility product constant (Ksp). The concentration of silver at the equivalence point is then calculated using Ksp, resulting in a significant increase from the previous concentration level. The p-value is also discussed, highlighting the change in silver concentration from the previous video.

Mindmap
Keywords
💡Titration Curve
A titration curve is a graphical representation that illustrates the changes in pH or concentration during a titration process. In the context of the video, the curve is used to identify the equivalence point, which is a critical moment in the reaction where the reactants are stoichiometrically equivalent, indicating the endpoint of the titration.
💡Equivalence Point
The equivalence point in a chemical titration is the point at which the amount of titrant added is stoichiometrically equivalent to the amount of analyte present in the solution. This is a critical point where the reaction is theoretically complete, and it is characterized by a sudden change in some measurable property, such as pH.
💡Millimoles
Millimoles (mmol) is a unit of measurement used in chemistry to express the amount of a substance. It is one-thousandth of a mole, a unit that represents the number of particles in a substance. Millimoles are particularly useful in dilute solutions or when dealing with small quantities of reactants, as in the case of the titration discussed in the video.
💡Stoichiometry
Stoichiometry is the study of the quantitative relationships between reactants and products in a chemical reaction. It is used to determine the amounts of substances involved in a reaction based on their chemical formulas and the balanced chemical equation. In the video, stoichiometry is used to understand the one-to-one ratio between moles of silver and chloride ions.
💡Concentration
Concentration in chemistry refers to the amount of a particular substance present in a given volume of a solution. It is typically expressed in moles per liter (M) or millimoles per milliliter (mmol/mL) and is a crucial factor in determining the rate of a reaction and the extent to which a reaction will proceed.
💡Silver Chloride (AgCl)
Silver chloride (AgCl) is a chemical compound formed by the reaction of silver ions (Ag+) with chloride ions (Cl-). It is a white, insoluble salt that is often used as a model system in solubility and precipitation reactions. In the video, the formation of AgCl is the goal of the titration reaction between silver and chloride ions.
💡Ksp (Solubility Product Constant)
The solubility product constant (Ksp) is a value that represents the maximum amount a compound can dissolve in water at a given temperature. It is used to predict the solubility of a compound and to determine if a precipitate will form in a solution. In the context of the video, Ksp is used to calculate the concentration of silver and chloride ions at the equivalence point.
💡Equilibrium
In chemistry, equilibrium refers to the state in which the concentrations of reactants and products remain constant over time, indicating that the forward and reverse reactions are occurring at the same rate. The concept of equilibrium is essential for understanding how reversible reactions behave and how they reach a state of balance.
💡pAg
The pAg is the negative logarithm (base 10) of the silver ion concentration in a solution. It is analogous to pH, which is the negative logarithm of the hydrogen ion concentration. pAg is used to express the activity or concentration of silver ions, and it is particularly relevant in the context of the video when discussing the equivalence point and the solubility of silver chloride.
💡pH
pH is a measure of the acidity or alkalinity of a solution, expressed as the negative logarithm (base 10) of the hydrogen ion concentration. It is a common parameter in chemistry and biochemistry, used to describe the reactive environment of a solution. In the context of titration, changes in pH can indicate the progress and endpoint of the reaction.
💡Molar Concentration
Molar concentration, often simply referred to as concentration, is the amount of a substance (solute) present in a given volume of solution, expressed in moles per liter (M). It is a fundamental concept in chemistry that relates the quantity of solute to the volume of solution, allowing for calculations of reaction stoichiometry and understanding of reaction dynamics.
Highlights

The equivalence point in titration is discussed, which is a critical concept in understanding reaction stoichiometry.

The calculation of millimoles of chloride is mentioned, which was found to be 2.5 millimoles.

The one-to-one stoichiometry between silver and chloride is emphasized, which is fundamental in determining the equivalence point.

The concentration of silver is given as 0.05 millimoles per milliliter, a key piece of information for further calculations.

A practical calculation is demonstrated to find the volume at the equivalence point, resulting in 50 milliliters.

The concept of concentration at the equivalence point is introduced, highlighting the reaction completion.

The solubility product constant (Ksp) is discussed, which governs the concentration of silver and chloride at the equivalence point.

An equilibrium problem from the previous chapter is referenced, showing the continuity of concepts in chemistry.

The method of treating the concentrations of silver and chloride as equal (x) at the equivalence point is explained.

The Ksp value is provided (1.8 times 10 to the minus 10), which is crucial for calculating concentrations at the equivalence point.

A step-by-step process for solving the concentration of silver at the equivalence point is outlined.

The concentration of silver at the equivalence point is calculated to be 1.34 times 10 to the minus 5 molar.

The p-value is introduced as a measure of concentration, with a lower p-value indicating a higher concentration.

A significant change in the concentration of silver is observed, moving from a p-value of 8.5 to 4.8 at the equivalence point.

The practical application of these calculations is emphasized, showing the dramatic change in silver concentration.

Transcripts

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ChemistryTitrationEquivalence PointSilver ConcentrationStoichiometrySolubility ProductKsp CalculationEducational ContentScientific ExplanationChemical Analysis