16 Questions
Which statement about acid-base indicators is correct?
They are weak organic acids or bases that slightly dissociate in aqueous solutions to form colored ions.
What is the purpose of a back titration technique?
To resolve problems encountered in direct titrations, such as slow titrations.
In a back titration, what is the role of the standardized NaOH solution?
It is the titrant of known concentration.
Which of the following is true about phenolphthalein as an indicator in acid-base titrations?
It is colorless in neutral solutions and pink in basic solutions.
In the experiment for determining ascorbic acid in vitamin C tablets, what role does phenolphthalein play?
It is the indicator used to determine the end point.
What is the significance of the equivalence point in an acid-base titration?
It is the point at which the moles of added titrant are stoichiometrically equal to the moles of analyte.
In an acid-base titration, what is the primary purpose of the indicator?
To determine the equivalence point by undergoing a color change
In the context of the back titration technique, what is the role of the standardized NaOH solution?
It serves as the titrant solution of known concentration
Which of the following statements accurately describes the relationship between the end point and the equivalence point in an acid-base titration?
The end point is located very close to the equivalence point
According to the Brønsted-Lowry theory, which of the following statements is true about weak acids and bases?
Weak acids and bases both partially dissociate in water
In the experiment for determining ascorbic acid (Vitamin C) in tablets, what is the role of phenolphthalein as the indicator?
It turns pink in the presence of excess NaOH
Which of the following statements accurately describes the role of the titrant in an acid-base titration?
The titrant is the solution of known concentration used to determine the unknown concentration
In the context of acid-base titrations, what is the primary purpose of performing a back titration?
To resolve issues related to slow titration rates or interference from other substances
According to the definition provided, which of the following statements accurately describes the analyte in an acid-base titration?
The analyte is the solution of unknown concentration being analyzed
Which of the following statements accurately describes the role of a strong acid or base in an acid-base titration?
Strong acids and bases are used as titrants due to their complete dissociation in water
In the context of acid-base indicators, what is the significance of the color change observed at the end point?
It indicates that the equivalence point has been reached
Study Notes
Titration
- A technique used to determine the concentration of an identified analyte by reacting it with a solution of known concentration (titrant)
- Involves adding a solution of known concentration from a burette to a measured volume of analyte
Analyte and Titrant
- Analyte: a solution of unknown concentration (known volume)
- Titrant: a solution of known concentration (volume obtained by titration)
Equivalence Point and End Point
- Equivalence point: the point at which the moles of added titrant are stoichiometrically equal to the moles of analyte
- End point: signals the end of titration where the indicator gives an observable change, located very close to the equivalence point
Acid-Base Chemistry
- Acid: a proton (H+) donor (Bronsted-Lowry definition)
- Base: a proton (H+) acceptor (Bronsted-Lowry definition)
- Strong acid/base: completely dissociates with water
- Weak acid/base: partially dissociates with water
Acid-Base Indicators
- Weak organic acids or bases that dissociate slightly in aqueous solutions to form ions
- Indicators change colors because their ions have colors that are different from undissociated molecules
- Example: phenolphthalein, a weak acid that is colorless in acidic and neutral solutions and pink in basic solutions
Acid-Base Titration
- A procedure used in quantitative analysis to determine the concentration of either an acid or a base
- Indicator should change sharply at the equivalence point
- At the end point of titration, all acids and bases are neutralized, and the flask contains water and salt only
Back Titration
- An alternative technique to direct titration designed to resolve some problems encountered in direct titration, such as slow titration
- Titrant: standardized NaOH solution
- Analyte: ascorbic acid (Vitamin C tablet samples)
- Indicator: phenolphthalein
This quiz covers the definition and key concepts of titration technique, where a solution of known concentration is used to determine the concentration of an unknown analyte. It includes information on analyte, titrant, equivalence point, and end point.
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