Summary of Ch.4-Stochiometry-Day3

Main Ideas and Concepts

• Acid-Base Neutralization Reactions:

  These reactions are a type of double replacement reaction where an acid reacts with a base to produce salt and water. The driving force behind these reactions will be discussed in detail later.

• Titration:

  A method used to determine the unknown concentration of an acid or base. An indicator is used to identify the endpoint of the Titration, which occurs when the moles of hydronium ions equal the moles of hydroxide ions.

• Setting Up a Titration:

  Use a burette filled with a solution of unknown concentration. A known volume of another solution is placed in a flask. As the Titration proceeds, a color change indicates the endpoint.

• Stoichiometry in Titration:

  Stoichiometric calculations are necessary to relate the moles of reactants and products. When converting between grams and moles, the molar mass from the periodic table is used.

• Standard Solutions and Standardization:

  Standard solutions are stable compounds used to ensure accurate concentrations. A common example is using Potassium Hydrogen Phthalate (KHP) to standardize Sodium Hydroxide (NaOH) solutions.

• Spectroscopy:

  A method to determine concentration using colorimetry or spectrophotometry. Colorimetry can be used for colored solutions, while spectrophotometry is suitable for colorless solutions. Beer’s Law relates absorbance to concentration and path length.

• Calibration Curves:

  Creating a calibration curve involves preparing standard solutions and measuring their absorbance. This curve allows for the determination of unknown concentrations based on absorbance measurements.

Methodology and Instructions

• Titration Setup:

  Fill a burette with the solution of unknown concentration. Measure a known volume of the titrant (known concentration) into a flask. Add an appropriate indicator to the flask. Gradually add the solution from the burette to the flask while observing for a color change to determine the endpoint.

• Stoichiometric Calculations:

  Convert grams of reactants to moles using molar mass. Use the balanced chemical equation to find the mole ratio. Calculate the moles of products formed from the moles of reactants. If needed, convert moles back to grams or volume using molarity.

• Standardization Process:

  Prepare a solution of approximate concentration. Use a stable standard compound (e.g., KHP) for Titration. Measure the volume of titrant used to reach the equivalence point and calculate the exact concentration of the unknown solution.

• Using a Colorimeter:

  Select the appropriate wavelength for maximum absorbance. Measure the absorbance of the sample and compare it to the calibration curve to find the concentration.

Speakers or Sources Featured

• Mrs. Middle (Instructor)

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