Padronização (parte 2 - cálculos e conceitos envolvidos): titulação de hidróxido de sódio (NaOH)

Summary

This video tutorial guides viewers through the process of standardizing a sodium hydroxide (NaOH) solution by titration. The host demonstrates how to determine the real concentration of a solution, explains the relevant chemical reactions, and provides a detailed walkthrough of the calculations involved. By using potassium biftalate as a reagent and employing stoichiometric relationships, viewers learn how to calculate molarity, molar mass, and volume to ensure precision. The tutorial emphasizes the importance of accurate measurements in chemistry experiments and the key concepts of molarity and titration.

Takeaways

• 😀 **Standardization of NaOH Solution**: The video discusses how to determine the actual concentration (molarity) of a sodium hydroxide (NaOH) solution through titration using potassium hydrogen phthalate (KHP).
• 😀 **Purpose of the Experiment**: The primary goal is to confirm whether the NaOH solution has a molarity of 0.1 M as originally intended by performing a titration with KHP.
• 😀 **Titration Process**: The instructor outlines the titration procedure where NaOH is gradually added to KHP until neutralization is reached, using phenolphthalein as an indicator.
• 😀 **Balanced Chemical Reaction**: The titration involves the neutralization of NaOH (a base) and KHP (an acid), following the reaction: NaOH + KHP → Water + Potassium Phthalate, with a 1:1 stoichiometric ratio.
• 😀 **Stoichiometric Ratio**: The video emphasizes the 1:1 molar ratio between NaOH and KHP in the neutralization reaction, which simplifies the calculations.
• 😀 **Key Data for Calculations**: The mass of KHP used in the experiment was 0.41 g, and 20 mL of NaOH was required to complete the titration.
• 😀 **Calculation of Moles of KHP**: The instructor demonstrates how to calculate the moles of KHP by dividing the mass of KHP (0.41 g) by its molar mass (204.22 g/mol), which results in 0.002 mol of KHP.
• 😀 **Moles of NaOH**: Since the reaction is 1:1, the moles of NaOH used in the titration are equal to the moles of KHP, which is 0.002 mol.
• 😀 **Formula for Molarity**: The molarity (M) of NaOH is calculated by dividing the moles of NaOH by the volume of NaOH in liters. For this experiment, the molarity is 0.1 M, matching the original concentration of NaOH.
• 😀 **Accuracy of Results**: The experiment successfully confirms the NaOH solution's molarity is 0.1 M, validating the preparation process of the solution and ensuring its accuracy.
• 😀 **Importance of Primary Standards**: KHP is highlighted as a reliable primary standard in titration experiments because of its purity and predictable reaction with NaOH, making it ideal for standardization.

Q & A

What is the purpose of the experiment described in the video?

The purpose of the experiment is to determine the true molarity (concentration) of a sodium hydroxide (NaOH) solution by standardizing it with a known solution of ammonia (NH₃) and potassium biftalate.

Why is standardization of solutions important in chemistry?

Standardization is important because it allows chemists to accurately determine the concentration of a solution, ensuring precise results in reactions and experiments.

What chemical reaction is involved in the titration described in the video?

The reaction involved is between ammonia (NH₃), a base, and potassium biftalate, an acidic substance. This reaction is used to determine the concentration of the ammonia solution through neutralization.

What stoichiometric ratio is used in the reaction between ammonia and potassium biftalate?

The stoichiometric ratio in the reaction is 1:1, meaning one mole of ammonia reacts with one mole of potassium biftalate.

What is the role of phenolphthalein in the experiment?

Phenolphthalein acts as an indicator. It turns pink when the ammonia neutralizes the potassium biftalate, signaling the end of the titration.

How is the molarity of the ammonia solution calculated?

The molarity of the ammonia solution is calculated using the formula: Molarity = moles of solute / volume of solution (in liters). The moles of ammonia are determined from the mass of potassium biftalate reacted and the molar masses involved.

What was the molar mass of potassium biftalate used in the calculations?

The molar mass of potassium biftalate was 204.22 g/mol, as provided in the video.

Why is the molarity of the ammonia solution important in the experiment?

The molarity of the ammonia solution is important because it helps to determine how much of the ammonia is required to neutralize a given amount of potassium biftalate. This enables accurate determination of the concentration of the NaOH solution.

What was the volume of ammonia solution used in the titration?

The volume of ammonia solution used in the titration was 20 mL, as indicated in the video.

What was the final result of the titration experiment regarding the ammonia solution’s molarity?

The final result of the titration showed that the molarity of the ammonia solution was 0.101 mol/L, which was very close to the target value of 0.1 mol/L.