Chemistry Standardization Methods

Questions and Answers

What is the primary purpose of volumetric analysis?

To determine the concentration of solutions (correct)

To measure the mass of a solid compound

To analyze the temperature of a reaction

To isolate chemical compounds from mixtures

Which step is NOT part of preparing a 0.1 N Sodium Hydroxide solution?

Heating the solution to 80°C (correct)

Diluting to volume in a volumetric flask

Dissolving in carbon dioxide free water

Weighing 4.5 grams of sodium hydroxide

What is the purpose of using potassium biphthalate in the standardization of the sodium hydroxide solution?

To lower the pH of the solution

To increase the volume of the solution

To act as a color indicator

To serve as a primary standard (correct)

What indicates the endpoint of the titration between sodium hydroxide and potassium biphthalate?

The appearance of a permanent pink color Signup and view all the answers

What initial treatment is necessary for potassium biphthalate before it is used in the standardization process?

It must be dried at 120°C for 2 hours Signup and view all the answers

When preparing a volumetric solution, what is the reason for using carbon dioxide free water?

To prevent the formation of carbonic acid Signup and view all the answers

During a neutralization reaction, what are the products formed?

Salt and water Signup and view all the answers

Which is a critical step to take after diluting the sodium hydroxide solution in a volumetric flask?

Store the solution in a properly labeled bottle Signup and view all the answers

What is the purpose of weighing anhydrous sodium carbonate before beginning the standardization of hydrochloric acid solution?

To ensure accurate preparation of the standard solution Signup and view all the answers

At what temperature should anhydrous sodium carbonate be heated prior to weighing?

270° C Signup and view all the answers

What indicator is used during the titration of hydrochloric acid solution in this experiment?

Methyl orange TS Signup and view all the answers

How much anhydrous sodium carbonate is equivalent to 1 mL of 1N hydrochloric acid?

52.99 mg Signup and view all the answers

What is the final color change expected when the titration with hydrochloric acid reaches the endpoint?

From yellow to orange Signup and view all the answers

Why is it necessary to repeat the titration procedure and conduct three trials?

To obtain an average result for accuracy Signup and view all the answers

Which of the following concentrations exceeds the handling precautions for hydrochloric acid?

40% HCl Signup and view all the answers

What is the primary aim of standardizing a hydrochloric acid solution?

To determine its exact normality Signup and view all the answers

Why is laboratory grade hydrochloric acid unsuitable as a primary standard?

It evaporates easily. Signup and view all the answers

What is the purpose of standardization in this experiment?

To determine the exact concentration of a solution. Signup and view all the answers

Which of the following steps is NOT part of preparing a 1N hydrochloric acid solution?

Measure the pH of the solution. Signup and view all the answers

What is the formula used to compute the normality of a solution?

Normality = gm/mEq x mL Signup and view all the answers

What type of solution is used to standardize hydrochloric acid in this experiment?

Sodium carbonate solution. Signup and view all the answers

Which procedure step should be done first when preparing the hydrochloric acid solution?

Pour distilled water into the volumetric flask. Signup and view all the answers

What does the term 'primary standard' refer to in this context?

A solid that is chemically pure (99%). Signup and view all the answers

Which property of sodium carbonate makes it suitable for standardizing hydrochloric acid?

It is chemically pure and stable. Signup and view all the answers

What is the purpose of an indicator in a titration?

To change color at the endpoint of the reaction Signup and view all the answers

What represents the endpoint in a titration process?

The completion stage of the reaction Signup and view all the answers

How is normality calculated based on the weight of potassium biphthalate?

Normality = grams/mEq x mL Signup and view all the answers

What is the significance of the equivalence point in titration?

It represents the stoichiometric balance between titrant and analyte Signup and view all the answers

What is the acceptable percentage range for sodium bicarbonate in tablets according to specifications?

95.0% to 105.0% Signup and view all the answers

What quantity does 1 mL of 0.1 N NaOH equate to in milligrams of potassium biphthalate?

204.23 mg Signup and view all the answers

In the purity determination formula, what does the denominator represent?

Weight of the sample analyzed Signup and view all the answers

What is the primary objective of performing a titration on sodium bicarbonate tablets?

To ascertain the purity or % label claim of sodium bicarbonate Signup and view all the answers

What visual change indicates the endpoint of the titration of sodium hydroxide with sulfuric acid?

From yellow to orange color Signup and view all the answers

What is the normality of the sulfuric acid solution prepared from 49.04 g of H2SO4 in 1000 mL?

1 N Signup and view all the answers

Which indicator is mentioned for use in standardizing sulfuric acid solution against sodium hydroxide?

Phenolphthalein Signup and view all the answers

What type of acid-base reaction occurs when sulfuric acid is titrated with sodium hydroxide?

Neutralization Signup and view all the answers

How much concentrated sulfuric acid is needed to prepare 1000 mL of a 1 N solution?

49.0 mL Signup and view all the answers

What is the pH of the resulting solution at the endpoint when titrating a strong acid with a strong base?

7.0 Signup and view all the answers

What is the outcome of titrating sulfuric acid with sodium hydroxide?

Sodium sulfate and water Signup and view all the answers

How many trials of titration should be performed during the standardization?

Three trials Signup and view all the answers

Study Notes

Preparation and Standardization of 1N Hydrochloric Acid Solution

Use 150 mg of anhydrous sodium carbonate, preheated at 270°C for 1 hour, for accurate results.
Dissolve sodium carbonate in 100 mL of distilled water and add 2 drops of methyl orange as an indicator.
Titrate until color changes from yellow to orange, indicating the endpoint.
Each 52.99 mg of sodium carbonate equals 1 mL of 1N hydrochloric acid.
Calculate normality using formula: Normality = gm/mEq x mL consumed in HCl solution.
Hydrochloric acid can be concentrated up to 40%, necessitating special handling due to evaporation.

Preparation and Standardization of 0.1N Sodium Hydroxide Solution

Weigh 4.5 grams of sodium hydroxide pellets and dissolve in carbon dioxide-free water.
Transfer to a 1 liter volumetric flask and dilute to volume with carbon dioxide-free water.
Store the prepared NaOH in a labeled 1L stock bottle.

Standardization of 0.1N Sodium Hydroxide Solution

Use 100 mg of potassium biphthalate, dried at 120°C for 2 hours, for standardization.
Dissolve in 75 mL carbon dioxide-free water and add 2 drops of phenolphthalein.
Titrate with NaOH until a permanent pink color is produced, indicating endpoint.
Each mL of 0.1N NaOH equates to 204.23 mg of potassium biphthalate.
Calculate normality using: Normality = gm/mEq x mL consumed in NaOH solution.

Assay of Sodium Bicarbonate Tablets

Aim to determine the purity or % label claim of sodium bicarbonate in tablets via direct titration.
Specification requires sodium bicarbonate tablets to contain 95.0% to 105.0% NaHCO3.
Use formula for computation:
- % Assay = (mL x N HCl x 84.01/1000) / Weight of Sample (grams) × 100.

Standardization of 0.1N Sulfuric Acid Solution

Run out 20 mL of 0.1N sodium hydroxide solution into a clean Erlenmeyer flask.
Add 2 drops of methyl orange and titrate with sulfuric acid until a color change occurs from yellow to orange.
Calculate normality of sulfuric acid after completing three trials.

Overview of Sulfuric Acid

Sulfuric acid is diprotic with a 1N solution containing 49.04 g H2SO4.
Approximately 49.0 mL of concentrated sulfuric acid is required to prepare 1000 mL of solution.
Alkalimetry occurs when a strong acid is titrated with a strong base, resulting in a neutral pH of 7.0 at the endpoint.
The standardization of sulfuric acid can use phenolphthalein as an indicator to observe endpoint.

Important Terms

Titrant: The substance in the burette used for titration.
Analyte: The titrand, typically a pure substance being analyzed.
Indicator: A chemical that changes color to signify the endpoint of a reaction.
Endpoint: The stage indicating reaction completion via color change.
Equivalence Point: Point in titration where the amount of titrant is stoichiometrically equivalent to the analyte.

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Description

This quiz focuses on the preparation and standardization techniques for hydrochloric acid and sodium hydroxide solutions. It covers detailed procedures, calculations of normality, and handling precautions for concentrated chemicals. Gain a deeper understanding of these essential laboratory practices.