ChemistryChapter 18: Alcohol
Acidity (weak)
Alcohols are very weak acids (weaker than water in some comparisons, book-dependent).
Learning objectives
- Explain acidity (weak) in simple chemical language.
- Connect 1. not carboxylic with 2. na metal using equations, observations, or trends where needed.
- Answer a short Federal Board question with the correct terms and a clear reason.
Definition
Alcohols are very weak acids (weaker than water in some comparisons, book-dependent). They do not fizz with carbonates (unlike carboxylic acids — a tell). Sodium metal: H2 and alkoxide named (school demo idea, not a sodium-handling SOP). Phenol more acidic than ethanol (named if in the book), still weak vs HCl. Meaning: OH of alcohols is not the carboxylic acid OH. ROH weak acid — H+ lost to strong base; alkoxide R-O- nucleophile. Primary alcohols need distillation to stop at aldehyde; dichromate colour change should be stated.
Important terms
- ACIDITY (WEAK)
- Alcohols are very weak acids (weaker than water in some comparisons, book-dependent).
- 1. NOT CARBOXYLIC
- No CO2 with Na2CO3.
- 2. Na METAL
- 2ROH + 2Na -> 2RONa + H2.
Overview
What they will not do, then Na:
Not Carboxylic
No CO2 with Na2CO3. pH near 7 in water. Litmus little change. Carboxylic acids later do fizz. Acidity primary > secondary > tertiary in gas phase; school compares ethanol vs water.
Examples Ethanol no CO2 · Ethanoic does · Sort the families
Na METAL
2ROH + 2Na -> 2RONa + H2. Alkoxide is a strong base (named). Safety: Na and alcohols — teacher demo, not a home experiment. Phenol more acidic than aliphatic alcohol — resonance stabilised phenoxide named.
Examples Alkoxide named · Strong base · Not a carbonate fizz
WHAT — ACIDITY (WEAK)
Alcohols are very weak acids (weaker than water in some comparisons, book-dependent). They do not fizz with carbonates (unlike carboxylic acids — a tell). Sodium metal: H2 and alkoxide named (school demo idea, not a sodium-handling SOP). Phenol more acidic than ethanol (named if in the book), still weak vs HCl. Meaning: OH of alcohols is not the carboxylic acid OH. ROH weak acid — H+ lost to strong base; alkoxide R-O- nucleophile. Primary alcohols need distillation to stop at aldehyde; dichromate colour change should be stated.
WHY — Why this topic matters
ACIDITY (WEAK) is an independent FBISE learning unit because students must use its definitions, conditions, equations, or trends separately in explanations and calculations.
HOW — How it works
NOT CARBOXYLIC: No CO2 with Na2CO3. pH near 7 in water. Litmus little change. Carboxylic acids later do fizz. Acidity primary > secondary > tertiary in gas phase; school compares ethanol vs water. Examples: Ethanol no CO2; Ethanoic does; Sort the families. Na METAL: 2ROH + 2Na -> 2RONa + H2. Alkoxide is a strong base (named). Safety: Na and alcohols — teacher demo, not a home experiment. Phenol more acidic than aliphatic alcohol — resonance stabilised phenoxide named. Examples: Alkoxide named; Strong base; Not a carbonate fizz. Exam tell alcohol vs acid: carboxylic acid + carbonate -> CO2 alcohol + carbonate -> no CO2 both may have OH in the formula, different groups
In simple words
Weak acidity. No sodium-metal how-to beyond the named equation.
Key points
- no fizz with carbonate
- Na metal: H2 named
- need COOH to fizz
- H2 gas
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Acidity (weak)
Sticky Notes · Quick Revision
Core Idea
- Alcohols are very weak acids (weaker than water in some comparisons, book-dependent). They do not fizz with carbonates (unlike carboxylic acids — a tell). Sodium metal: H2 and alkoxide named (school demo idea, not a sodium-handling SOP). Phenol more acidic than ethanol (named if in the book), still weak vs HCl. Meaning: OH of alcohols is not the carboxylic acid OH. ROH weak acid — H+ lost to strong base; alkoxide R-O- nucleophile. Primary alcohols need distillation to stop at aldehyde; dichromate colour change should be stated.
1. NOT CARBOXYLIC
- No CO2 with Na2CO3. pH near 7 in water. Litmus little change. Carboxylic acids later do fizz. Acidity primary > secondary > tertiary in gas phase; school compares ethanol vs water.
- Ethanol no CO2
- Ethanoic does
- Sort the families
2. Na METAL
- 2ROH + 2Na -> 2RONa + H2. Alkoxide is a strong base (named). Safety: Na and alcohols — teacher demo, not a home experiment. Phenol more acidic than aliphatic alcohol — resonance stabilised phenoxide named.
- Alkoxide named
- Strong base
- Not a carbonate fizz
Exam Example
- Exam tell alcohol vs acid:
- carboxylic acid + carbonate -> CO2
- alcohol + carbonate -> no CO2
- both may have OH in the formula, different groups
Common Misconceptions
- Do not confuse 1. NOT CARBOXYLIC with 2. Na METAL; state the difference before giving an example.
- Writing only “no fizz with carbonate” is not enough. Explain what it means in a complete sentence.
FBISE Exam Check
- Explain acidity (weak), compare its two main parts, and include the correct chemical evidence.
- Weak acidity. No sodium-metal how-to beyond the named equation.
60-second revision
- Alcohols are very weak acids (weaker than water in some comparisons, book-dependent).
- 1. NOT CARBOXYLIC: No CO2 with Na2CO3.
- 2. Na METAL: 2ROH + 2Na -> 2RONa + H2.
- Exam reminder: Exam tell alcohol vs acid: carboxylic acid + carbonate -> CO2 alcohol + carbonate -> no CO2 both may have OH in the formula, different groups
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