How to do a titration and calculate the concentration

Ivan Kahl
10 Sept 201509:41
EducationalLearning
32 Likes 10 Comments

TLDRThis instructional video demonstrates the process of a titration experiment to determine the concentration of an unknown substance. It outlines the necessary equipment, including a burette, beakers, a conical flask, and phenolphthalein as an indicator. The tutorial covers the initial setup, including rinsing apparatus and filling the burette with the titrant, NaOH. It then guides through the titration steps, emphasizing the importance of careful observation for the endpoint. Finally, it explains how to calculate the concentration of the unknown acid, HCl, using the balanced chemical equation and the average volume change from multiple titrations.

Takeaways
  • πŸ”¬ A titration is an experiment used to determine the concentration of an unknown substance.
  • πŸ§ͺ The main apparatus needed for a titration includes a pipette, beakers, a burette, a conical flask, a white tile, and phenolphthalein as an indicator.
  • πŸ’§ Deionized water is used to rinse the apparatus to avoid any reactions.
  • πŸ“ It's crucial to ensure the burette is closed to prevent the flow of the known substance, NaOH in this case.
  • πŸ“ The pipette is used to measure 25 mL of the unknown substance, HCl, accurately.
  • πŸ“‰ The initial reading of the burette is taken before starting the titration to three decimal places using a white tile for contrast.
  • 🌈 Phenolphthalein indicator is added to the unknown solution to observe the color change during titration.
  • 🀲 When titrating, the burette is held with one hand while the other hand controls the conical flask to add the known substance drop by drop.
  • πŸ”΄ The endpoint of the titration is reached when the pink color of the phenolphthalein stays, indicating the reaction is complete.
  • πŸ“Š After performing multiple titrations, an average change in volume can be calculated to determine the concentration of the unknown solution.
  • βš–οΈ A balanced chemical equation is created to understand the reaction between the acid (HCl) and the base (NaOH), forming a salt (NaCl) and water (H2O).
  • πŸ“š The concentration of the unknown acid is calculated using the formula and the average volume change from the titrations, resulting in a concentration of 0.05 moles per decimeter cubed.
Q & A

  • What is the purpose of a titration?

    -A titration is used to calculate the concentration of an unknown substance by reacting it with a known substance of known concentration.

  • What apparatus is needed for a titration experiment?

    -The necessary apparatus includes a burette, a beaker for the titrant (NaOH in this case), a beaker for the titrand (HCl in this case), a conical flask, a white tile, a dropper, phenolphthalein as an indicator, and a retort stand.

  • Why is it important to rinse the apparatus before starting the titration?

    -Rinsing the apparatus with deionized water is crucial to avoid any contamination that could affect the accuracy of the titration results.

  • Why should the burette not be cleaned before filling it with the titrant?

    -The burette should not be cleaned because cleaning it could introduce water into the titrant, which would dilute the solution and affect the titration results.

  • How is the burette filled with the titrant?

    -The burette is filled by ensuring it is closed, then filling it with the titrant (NaOH in this case), and making sure it is at a reading, not necessarily at zero.

  • What is the purpose of using a white tile during the titration?

    -The white tile is used to provide a clear background against which the color change of the solution can be observed, which is essential for determining the endpoint of the titration.

  • How many drops of phenolphthalein are added to the titrand?

    -Three drops of phenolphthalein are added to the titrand (HCl in this case).

  • What is the initial reading taken from the burette before starting the titration?

    -The initial reading is taken from the burette by placing a white tile behind it and measuring from the bottom of the concave meniscus to three decimal places.

  • How is the titration performed?

    -The titration is performed by holding the burette tap with one hand, spinning the conical flask with the other hand, and slowly adding the titrant drop by drop until the endpoint is reached, indicated by a persistent pink color.

  • How is the concentration of the unknown solution calculated after the titration?

    -The concentration of the unknown solution is calculated by using the balanced chemical equation, the volume of the titrant used, and the concentration of the titrant. The formula involves the moles of acid reacting with moles of base to form a salt and water.

  • What was the average volume change obtained after three titrations in the script?

    -The average volume change obtained after three titrations was 13.66 mL.

  • How is the concentration of the acid determined from the titration results?

    -The concentration of the acid (HCl) is determined by dividing the product of the volume of the acid and the concentration of the base (NaOH) by the volume of the acid used in the titration.

Outlines
00:00
πŸ§ͺ Setting Up for a Chemistry Titration Experiment

This paragraph introduces the process of a titration experiment, which is used to determine the concentration of an unknown substance. The narrator lists the necessary apparatus including a 25 ml burette, beakers, a conical flask, a white tile, a burette stand, and phenolphthalein as an indicator. The importance of rinsing all apparatus with deionized water is emphasized to avoid reactions. The burette is filled with the known substance, NaOH, and care is taken to ensure it's closed to prevent leakage. A 25 ml volume of the unknown substance, HCl, is measured using a burette and transferred to the conical flask. The narrator also explains the procedure for adding the indicator and taking initial readings with the burette, setting the stage for the titration process.

05:03
πŸ“Š Conducting the Titration and Calculating Concentration

In this paragraph, the actual titration process is described, where the known substance (NaOH) is added dropwise to the unknown substance (HCl) in the conical flask until the endpoint is reached, indicated by the persistent pink color due to phenolphthalein. The narrator explains how to handle the burette and conical flask to ensure accurate titration. After completing the titration, the final volume reading of the burette is taken to calculate the change in volume. The average change in volume from three titrations is determined to be 13.66 ml. Using a balanced chemical equation (HCl + NaOH β†’ NaCl + H2O), the narrator demonstrates how to calculate the concentration of the unknown acid (HCl) by substituting the known values into the formula. The calculation concludes with the concentration of the acid being approximately 0.05 moles per decimeter cubed, rounded to two decimal places.

Mindmap
Keywords
πŸ’‘Titration
Titration is a laboratory technique used to determine the concentration of an unknown substance by reacting it with a solution of known concentration. In the video, the process of titration is demonstrated to find out the concentration of hydrochloric acid (HCl) using a known concentration of sodium hydroxide (NaOH). The video script describes the setup and procedure for a titration experiment, emphasizing the importance of apparatus such as a burette and a conical flask.
πŸ’‘Apparatus
Apparatus refers to the set of equipment used in a scientific experiment or procedure. In the context of the video, the term is used to list the necessary items for conducting a titration, including a burette, beakers, a conical flask, a white tile, a dropper, and a retort stand. The apparatus is crucial for the accurate execution of the titration process.
πŸ’‘Concentration
Concentration in chemistry is a measure of the amount of a substance contained in a given volume of solution. The video's main objective is to calculate the concentration of an unknown substance, which is HCl in this case, by using a titration with a substance of known concentration, NaOH. The script explains how the average change in volume from multiple titrations is used to determine the concentration of the unknown substance.
πŸ’‘Indicator
An indicator is a substance that changes color in response to changes in pH, and it is used in titrations to signal the endpoint of the reaction. In the video, phenolphthalein is mentioned as the indicator for the titration between NaOH and HCl. The script describes adding three drops of phenolphthalein to the HCl solution to observe the color change that indicates the endpoint of the titration.
πŸ’‘Endpoint
The endpoint of a titration is the point at which the reaction between the titrant and the titrand is considered complete. The video script explains how the color change of the indicator (phenolphthalein turning pink) signifies the endpoint of the titration between NaOH and HCl, indicating that the reaction has reached a certain pH level where the color change occurs.
πŸ’‘Burette
A burette is a piece of laboratory apparatus used to deliver a precise volume of liquid. In the video, a burette is filled with the titrant (NaOH) and is used to slowly add it to the titrand (HCl) in the conical flask. The script details the importance of the burette being closed to prevent the NaOH from flowing out and the process of filling it with the known solution.
πŸ’‘Titrand
The titrand is the substance whose concentration is being determined in a titration. In the video script, the titrand is hydrochloric acid (HCl), which is of unknown concentration. The script describes the process of measuring a precise volume of the titrand using a pipette and adding it to a conical flask for the titration.
πŸ’‘Titrant
The titrant is a solution of known concentration that is used to titrate another solution in a titration process. In the video, the titrant is sodium hydroxide (NaOH) with a known concentration, which is used to determine the concentration of the titrand, hydrochloric acid (HCl). The script explains how the titrant is filled into the burette for the titration.
πŸ’‘Balanced Equation
A balanced chemical equation represents a chemical reaction where the number of atoms for each element is equal on both sides of the equation. In the video, a balanced equation is used to understand the stoichiometry of the reaction between NaOH and HCl, which forms a salt (NaCl) and water (H2O). The script provides an example of how to balance the equation and use it in the calculation of the unknown concentration.
πŸ’‘Moles
Moles are a measure used in chemistry to express amounts of a chemical substance, based on Avogadro's number. In the context of the video, moles are used in the balanced equation to understand the relationship between the reactants (NaOH and HCl) and the products (NaCl and H2O). The script explains how the moles of acid and base are used in the calculation to determine the concentration of the unknown substance.
πŸ’‘Decim Cubed
Decim cubed (dmΒ³) is a unit of volume equivalent to a liter. In the video, the term is used to describe the volume of the solutions being measured and titrated. The script mentions measuring volumes in cmΒ³ but clarifies that the unit does not affect the ratio used in the calculations, as the concentration is determined by the ratio of volumes, not the absolute volume.
Highlights

Introduction to the process of titration for calculating the concentration of an unknown substance.

List of necessary apparatus for the titration experiment including a petri dish, beakers, a burette, a conical flask, and a white tile.

The importance of rinsing all apparatus with deionized water to avoid reactions.

Filling the burette with the known substance, NaOH, and ensuring it's closed to prevent leakage.

Using a 25 mL pipette to accurately measure the unknown substance, HCl, into the conical flask.

Adding phenolphthalein as an indicator to the titrand to observe color changes during the titration.

The method to record the initial volume reading from the burette using a white tile for clarity.

Technique for slowly adding the titrant to the titrand while observing for theζŒδΉ… pink color change.

Final volume reading from the burette to determine the change in volume during titration.

Performing multiple titrations to obtain an average change in volume for more accurate calculations.

Creating a balanced chemical equation for the reaction between HCl and NaOH to form NaCl and H2O.

Using the balanced equation and the stoichiometry to calculate the concentration of the unknown acid.

Explanation of how to manipulate the formula to solve for the unknown concentration of the acid.

Final calculation revealing the concentration of the unknown acid as 0.05 moles per decimeter cubed.

Clarification on the use of decimeters cubed versus centimeters cubed and the irrelevance due to the ratio used in calculations.

Summary of the titration process, emphasizing the importance of accuracy and observation for successful results.

Transcripts

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Titration MethodChemistry LabConcentration CalculationLab ApparatusExperiment ProcessChemical ReactionIndicator UseVolume MeasurementAcid Base ReactionEducational Guide