16 Questions
Match the following solvents with their characteristic:
Aprotic solvents = Do not accept or donate H+ Amphiprotic solvents = Act as acids or bases Protogenic solvents = Have a leveling effect on weak bases Protophillic solvents = Have a leveling effect on weak acids
Match the following types of solvents with their examples:
Aprotic solvents = Benzene Amphiprotic solvents = Methanol Protogenic solvents = Hydrochloric acid Protophillic solvents = Liquid ammonia
Match the following reagents with their uses in non-aqueous titration:
Glacial acetic acid = Solvent for titrating basic substances Acetous perchloric acid = Titrant for titrating basic substances Crystal violet = Indicator for titrating basic substances Acetic anhydride = Reagent for acetylating amines
Match the following reactions with their equations:
Primary amine with acetous perchloric acid = RNH2 + HClO4 → RNH3+ + ClO4- Secondary amine with acetous perchloric acid = R2NH + HClO4 → R2NH2+ + ClO4- Tertiary amine with acetous perchloric acid = R3N + HClO4 → R3NH+ + ClO4- Primary amine with acetic anhydride = RNH2 + (CH3CO)2O → RNHCOCH3 + CH3COOH
Match the following applications with their descriptions:
Determination of basic substances = Titrating amines with acetous perchloric acid Determination of tertiary amine only = Acetylating amines with acetic anhydride Non-aqueous titration = Titration using solvents other than water Dielectric constant = Ability to separate positively and negatively charged ions
Match the following solvents with their dielectric constants (D):
Water (H2O) = D = high Ethanol = D = low Glacial acetic acid = D = high Hexane = D = low
Match the following indicators with their color changes:
Crystal violet = Violet (basic) to bluish green (acidic) Phenolphthalein = Colorless (acidic) to pink (basic) Methyl orange = Yellow (acidic) to red (basic) Bromothymol blue = Yellow (acidic) to blue (basic)
Match the following amines with their reactions:
Primary amine = RNH2 + HClO4 → RNH3+ + ClO4- Secondary amine = R2NH + HClO4 → R2NH2+ + ClO4- Tertiary amine = R3N + HClO4 → R3NH+ + ClO4- Mixture of amines = Acetylated with acetic anhydride
Match the following properties of solvents in non-aqueous titrations with their descriptions:
Relative acidity and basicity = The ability of a solvent to increase the strength of weak acids or weak bases Levelling effect = The ability of a solvent to differentiate between the strength of acids or bases Differentiating effect = The ability of a solvent to increase the strength of weak acids or weak bases Autoprotolysis = The ability of a solvent to behave as an acid or a base relative to the substance
Match the following substances with their behavior in a particular solvent:
Potassium acid phthalate = Acts as a base in glacial acetic acid Acetic acid = Acts as a base in pyridine Amines = Behave as strong acids in glacial acetic acid Weak carboxylic acids = Behave as weak acids in liquid ammonia
Match the following solvents with their effect on weak acids or weak bases:
Glacial acetic acid = Increases the strength of weak acids Liquid ammonia = Increases the strength of weak bases Pyridine = Differentiates between the strength of mineral acids Water = Has a levelling effect on weak acids and weak bases
Match the following effects of solvents with their examples:
Levelling effect = Acetic acid behaving as a base in perchloric acid Differentiating effect = Glacial acetic acid differentiating between the strength of mineral acids Relative acidity and basicity = Amines behaving as strong bases in glacial acetic acid Autoprotolysis = Glacial acetic acid having a levelling effect on weak bases
Match the following equations with their descriptions:
HA + HA ↔ [A- HAH +] ↔ A- + H2A+ = Autoprotolysis reaction of a solvent Ks = [A-] [H2A+] = Equation for the levelling effect of a solvent A- + H2A+ → HA + HA = Reverse reaction of autoprotolysis Ks = [H2A+] / [A-] = Equation for the differentiating effect of a solvent
Match the following solvents with their characteristics:
Glacial acetic acid = Basic solvent Liquid ammonia = Acidic solvent Pyridine = Basic solvent Water = Neutral solvent
Match the following statements with their correctness:
Glacial acetic acid has a levelling effect on weak acids = False Liquid ammonia has a differentiating effect on weak bases = False Acetic acid behaves as a base in pyridine = True Water has a levelling effect on weak acids and weak bases = False
Match the following terms with their definitions:
Autoprotolysis = The ability of a solvent to differentiate between the strength of acids or bases Levelling effect = The ability of a solvent to behave as an acid or a base relative to the substance Differentiating effect = The self-dissociation reaction of a solvent Relative acidity and basicity = The ability of a solvent to increase the strength of weak acids or weak bases
Study Notes
Neutralization Reactions in Non-Aqueous Medium
- Neutralization reactions in non-aqueous medium involve titration in a medium free from water, mainly used for determining weak acids and weak bases.
Properties of Solvents in Non-Aqueous Titrations
- Relative acidity and basicity of a substance are relative to the solvent.
- A substance behaves as an acid when dissolved in a less acidic solvent and as a base when dissolved in a more acidic solvent.
Levelling Effect
- Ability of solvent to increase the strength of weak acids or weak bases to reach the level of strong acid or base respectively.
- Acidic solvents have levelling effect on weak bases, and basic solvents have levelling effect on weak acids.
Differentiating Effect
- Ability of solvent to differentiate between the strength of acids or bases.
- Glacial acetic acid differentiates between the strength of mineral acids.
Autoprotolysis (Ks)
- Self-dissociation reaction of solvent.
- Good solvent should have small Ks to minimize the production of ionic species that compete with the substance to be determined.
Dielectric Constant (D)
- Ability to separate positively charged ions from negatively charged ions.
- Good solvent should have high D to ensure completeness of reactions.
Types of Solvents Used in Non-Aqueous Titrations
- Aprotic solvents: neutral, inert, do not accept or donate H+, have no autoprotolytic and no levelling effect. Examples: Hydrocarbons, Benzene, CHCl3, CCl4, and nitrobenzene.
- Amphiprotic solvents: act as acids or bases, may donate or accept H+.
Applications of Non-Aqueous Titration
- Determination of basic substances: use glacial acetic acid as solvent and acetous perchloric acid as titrant.
- Determination of tertiary amine only: sample is refluxed with acetic anhydride to acetylate primary and secondary amines.
This quiz covers neutralization reactions in non-aqueous mediums, focusing on titration methods for determining weak acids and bases in solvents other than water.
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