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Questions and Answers
Why are strong acids or strong bases used as standard solutions in neutralization titrations?
Why are strong acids or strong bases used as standard solutions in neutralization titrations?
What is the advantage of using dilute hydrochloric acid solutions as standard solutions?
What is the advantage of using dilute hydrochloric acid solutions as standard solutions?
Why are standard solutions of nitric acid seldom used?
Why are standard solutions of nitric acid seldom used?
What is the final step in obtaining a standard acid solution?
What is the final step in obtaining a standard acid solution?
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What is the most frequently used reagent for standardizing acids?
What is the most frequently used reagent for standardizing acids?
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What is the most common base used for preparing standard solutions?
What is the most common base used for preparing standard solutions?
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What is the purpose of sparging in standardizing bases?
What is the purpose of sparging in standardizing bases?
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What is the result of absorption of carbon dioxide by a standardized solution of sodium or potassium hydroxide?
What is the result of absorption of carbon dioxide by a standardized solution of sodium or potassium hydroxide?
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What is a characteristic of potassium hydrogen phthalate as a primary standard?
What is a characteristic of potassium hydrogen phthalate as a primary standard?
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Why is it necessary to remove carbonate ions from standard base solutions?
Why is it necessary to remove carbonate ions from standard base solutions?
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Study Notes
Neutralization Titrations
- Strong acids or strong bases are used as standard solutions in neutralization titrations because they react more completely with an analyte and produce a larger change in pH at the equivalence point.
Standard Acid Solutions
- Hydrochloric acid (HCl) is widely used as a standard solution for titrating bases.
- Dilute HCl solutions are stable indefinitely.
- Many chloride salts are soluble in aqueous solutions.
- Solutions of 0.1 M HCl can be boiled for up to an hour without acid loss as long as evaporated water is replaced.
Preparation of Standard Acid Solutions
- Steps to obtain a standard acid solution:
- Prepare a solution of an approximate concentration by diluting the concentrated agent.
- Standardize the diluted acid solution against a primary-standard base or occasionally use density measurements.
- Weigh a quantity of the concentrated acid and dilute it to a known volume.
Preparation of Constant-Boiling HCl
- A stock solution with a known HCl concentration can be prepared by diluting a quantity of the concentrated reagent with an equal volume of water followed by distillation.
- The final quarter of the distillate (constant-boiling HCl) has a constant and known composition.
- The acid content of constant-boiling HCl depends only on atmospheric pressure.
Primary Standards for Acids
- Sodium carbonate is the most frequently used reagent for standardizing acids.
- Tris-(hydroxymethyl)aminomethane (TRIS) is also a common primary standard for acids.
- Sodium tetraborate decahydrate and mercury (II) oxide have also been recommended.
Preparation of Standard Solutions of Base
- Sodium hydroxide is the most common base for preparing standard solutions.
- Potassium hydroxide and barium hydroxide are also used.
- Absorption of carbon dioxide by a standardized solution of sodium or potassium hydroxide leads to a negative systematic error (the carbonate error) in analyses.
Removing Carbonate Ion from Standard Base Solutions
- Carbonate ion in standard base solutions decreases the sharpness of end points and is usually removed before standardization.
- Sparging is the process of removing a gas from a solution by bubbling an inert gas, such as air, through the solution.
Standardization of Bases
- Most primary standards used to standardize bases are weak organic acids that require the use of an indicator with a basic transition range.
- Potassium hydrogen phthalate is a nearly ideal standard.
- Other primary standards include benzoic acid and potassium hydrogen iodate.
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Description
This quiz covers the use of strong acids and bases as standard solutions in neutralization titrations, including the advantages of hydrochloric acid solutions.
