Conductometric Titration: Strong and Weak Acids

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Questions and Answers

What is the underlying principle upon which conductometric titration is based?

  • The fact that ions are replaced by others during the titration, leading to a change in conductivity. (correct)
  • The change in temperature during the filtration process.
  • The solution remains the same during the titration.
  • The constant conductivity of ions throughout the titration.

During conductometric titration, the equivalence point can only be determined through chemical indicators, not graphically.

False (B)

During the titration of a strong acid with a strong base, there is a decrease in ______ as highly mobile hydrogen ions (H+) are replaced by sodium ions (Na+).

conductivity

What two processes are being followed when a mixture of a strong acid (like HCl) and a weak acid (like CH3COOH) is titrated against a strong base?

<p>HCl reacts first, followed by CH3COOH</p> Signup and view all the answers

Match the changes in conductivity with the stages of titrating a mixture of strong and weak acids with a strong base:

<p>Initial Stage (Strong Acid Titration) = Conductivity decreases as highly mobile H+ ions are replaced. Mid-Stage (Weak Acid Titration) = Conductivity increases slightly as the less mobile acetate ions replace the unionized weak acid. After Equivalence Point = Conductivity increases significantly as excess hydroxide ions are added.</p> Signup and view all the answers

What type of solution is prepared to standardize it using a primary standard like oxalic acid?

<p>0.1N Sodium Hydroxide (D)</p> Signup and view all the answers

When preparing solutions of acetic acid and hydrochloric acid for conductometric titration, the mass of components is not important as long as the volume is maintained.

<p>False (B)</p> Signup and view all the answers

What piece of equipment needs to be washed with distilled water and immersed in the solution when setting up the conductivity meter?

<p>Conductivity cell</p> Signup and view all the answers

During the standardization of NaOH using oxalic acid, concordant readings are essential for calculating the ______ of the NaOH solution.

<p>strength</p> Signup and view all the answers

Match the formula with the appropriate definitions:

<p>$N_1V_1 = N_2V_2$ = Formula used to calculate the strength of NaOH. $N_1$ = Strength of oxalic acid. $V_1$ = Volume of oxalic acid. $N_2$ = Strength of NaOH. $V_2$ = Volume of NaOH consumed.</p> Signup and view all the answers

In the standardization of acetic acid using NaOH, what does 'IBR' stand for when recording data?

<p>Initial Burette Reading (C)</p> Signup and view all the answers

The calculated strength of acetic acid ($N_1$) is directly proportional to the volume of acetic acid ($V_1$). That is, as $V_1$ increases, $N_1$ also increases.

<p>False (B)</p> Signup and view all the answers

In the context of standardizing HCl using NaOH, what is being determined when this titration is performed?

<p>Strength of HCl</p> Signup and view all the answers

In calculations for the standardization of a reagent, concordant readings from multiple titrations increase the ______ of the results.

<p>accuracy</p> Signup and view all the answers

For the titration of a mixture of acids, associate each point on the conductometric titration curve with the corresponding chemical process:

<p>Initial steep decrease in conductance = Neutralization of the strong acid (HCl). Gradual increase in conductance = Neutralization of the weak acid (CH3COOH). Sharp increase in conductance after the equivalence points = Excess addition of the strong base (NaOH).</p> Signup and view all the answers

What is the significance of the point where the curve changes direction on a conductometric titration graph?

<p>Indicates the equivalence point where the reaction is complete. (D)</p> Signup and view all the answers

The volume of NaOH required for the neutralization of acetic acid is greater than the volume of NaOH required for the neutralization of HCl in the experiment.

<p>False (B)</p> Signup and view all the answers

Which point on the titration curve represents the neutralization point of hydrochloric acid?

<p>Point B</p> Signup and view all the answers

According to the graph provided, the curve after point C is due to the presence of excess ______.

<p>NaOH</p> Signup and view all the answers

Match the process occurring during conductometric titration with the corresponding effect on conductivity of the solution:

<p>Replacement of H+ ions with Na+ ions = Decrease in conductivity. Neutralization of acetic acid = Slight increase in conductivity. Addition of excess NaOH = Steep increase in conductivity.</p> Signup and view all the answers

Why is distilled water preferable to tap water for preparing solutions in conductometric titrations?

<p>Tap water may contain ions that interfere with conductivity measurements. (B)</p> Signup and view all the answers

Since the experiment involves acids and bases, it is acceptable to dispose of waste solutions directly into a regular drain without neutralization or special treatment.

<p>False (B)</p> Signup and view all the answers

What is the main reason for using a burette in conductometric titration rather than simply adding the titrant from a beaker?

<p>Accurate measurements of the amount of base</p> Signup and view all the answers

In the conductometric titration experiment involving both strong and weak acid, the ______ of the weak acid starts only after the point where all of the strong acid is consumed.

<p>neutralization</p> Signup and view all the answers

Match the experimental step with its primary purpose:

<p>Washing the conductivity cell with distilled water = Ensuring no contaminants affect readings. Standardizing the NaOH solution = Determining the exact concentration of the titrant. Plotting conductance versus volume of NaOH = Graphical detemination of the end point.</p> Signup and view all the answers

Which of the following describes the consequence to the results if the concentration of the NaOH titrant has changed during the experiment?

<p>The determined concentrations of the acids will be inaccurate. (A)</p> Signup and view all the answers

A rough initial titration is unnecessary because accurate readings ensure the integrity of the data, making any preliminary approximation redundant.

<p>False (B)</p> Signup and view all the answers

If air bubbles are present in the burette tip during a conductometric titration, how will this affect the accuracy of the experiment?

<p>Inaccurate readings</p> Signup and view all the answers

When performing conductometric titrations, always record readings after ______ have been added to ensure reliable data.

<p>each increment</p> Signup and view all the answers

Associate each item of laboratory apparatus used with its specific role in performing conductometric titrations:

<p>Conductometer = Measures the electrical conductance of the solution. Burette = Accurately dispenses the titrant. Beaker = Contains the solution being titrated. Glass Rod = Used for stirring the solution to ensure homogeneity.</p> Signup and view all the answers

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Flashcards

Conductometric Titration

Titration based on measuring changes in electrical conductivity.

Acid Mixture

A mixture containing both a strong acid and a weak acid.

Conductometer

Instrument used to measure a solution's electrical conductivity.

Ion Replacement

Replaces one ion with another during titration, affecting ionic conductivity.

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Equivalence Point

Point in titration where the amount of titrant is stoichiometrically equal to the analyte.

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H+ to Na+ Replacement

Mobile hydrogen ions are replaced by sodium ions during titration.

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Weak Acid Ionization

After strong acid is consumed, weak acid ionization increases.

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Step Increase

A sudden change in conductivity indicates the end point.

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Hydroxide Ions

Moving hydroxide ions cause a step increase in conductivity.

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Standardization

Process to accurately determine the concentration of a solution.

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Primary Standard

Solution with a precisely known concentration, used in standardization.

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Study Notes

  • In conductometric titration, the aim is to titrate a mixture of a strong and weak acid.

Apparatus Required

  • Conductometer
  • Conductance Cell
  • Burette
  • Pipette
  • Beaker
  • Standard flask
  • Glass rod
  • Burette Stand

Chemicals Required

  • Distilled Water
  • Hydrochloric acid
  • Sodium hydroxide
  • Oxalic acid

Theory of Conductometry

  • Conductometry titration is based on the principle that, during titration, one ion is replaced by another.
  • The two ions differ in ionic conductivity, resulting in a conductivity change in the solution during titration.
  • The equivalence point can be located graphically by plotting the change in conductance as a function of the volume of titrant added.
  • A mixture of a strong acid (HCl) and a weak acid (CH3COOH) is titrated against a strong base (NaOH).
  • HCl reacts first, followed by CH3COOH.
  • As a strong base is added, the highly mobile hydrogen ions (H+) are replaced by sodium ions (Na+), decreasing conductivity.
  • The reaction is: NaOH + HCl → NaCl + H2O
  • Once all the strong acid is consumed, the base reacts with the weak acid, increasing conductivity as unionized weak acid becomes ionized salt.
  • The reaction is: CH3COOH + Na+ + OH- → CH3COO- + H+ + Na+ + OH-
  • After both acids are consumed, there is a step increase in conductivity, indicating the endpoint.
  • The increase in conductivity is due to the fast-moving hydroxide ions from the burette solution.
  • From this, the amount of base consumed in the neutralization of HCl and CH3COOH is calculated.

Procedure

  • Preparation of Solution
  • Prepare 100ml of 0.1N NaOH solution and standardize it using a primary standard like oxalic acid.
  • Prepare 100ml of 0.1N acetic acid and 0.01N oxalic acid solution and 0.1N HCl solution by dissolving a known weight in distilled water.
  • Setting up the Conductivity meter
  • Wash the conductivity cell with distilled water and immerse it in the solution.
  • Connect the conductivity meter and calibrate it.

Standardization of NaOH Using Oxalic Acid

  • N1 (Strength of oxalic acid) ≈ 0.01N
  • V1 (Volume of oxalic acid) = 10ml
  • N2 (Strength of NaOH) = ?
  • V2 (Volume of NaOH consumed)
  • N1V1 = N2V2
  • N2 = (N1V1) / V2
  • N2 = (0.01 * 10) / 1.1 = 0.09N

Standardization of Acetic Acid Using NaOH

  • N1 (Strength of acetic acid) = ?
  • V1 (Volume of acetic acid) = 10 ml
  • N2 (Strength of NaOH) = 0.09N
  • V2 (Volume of NaOH consumed)
  • N1V1 = N2V2
  • N1 = (N2V2) / V1 = (0.09 * 11) / 10 = 0.099N

Standardization of HCl Using NaOH

  • N1 (Strength of HCl) = ?
  • V1 (Volume of HCl) = 10ml
  • N2 (Strength of NaOH) = 0.09N
  • V2 (Volume of NaOH consumed)

Conductometry Titration Data

  • Graphs show conductance (ms) vs Volume of NaOH (ml) during titration.
  • 3.5 ml volume of NaOH is needed for the neutralization of HCl.
  • 2.5 ml volume of NaOH is needed for the neutralization of acetic acid.
  • Point B represents the neutralization point of HCl.
  • Point C represents the neutralization point of acetic acid.
  • The curve after point C is due to NaOH.

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