What are chemical pentanoic acid equations

Alkanoic acids

Note

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Physics. and chemical properties of alkanoic acids

work in groups

Group 1: Boiling temperatures of alkanoic acids

Solve the set tasks in your group. You have 20 minutes for this. Enter the results on the slide. Choose a group speaker to present your results.

Tasks:

  1. Describes the dependence of the boiling temperatures on the length of the carbon chain shown in the diagram. Establish the connection.
  2. Compares the boiling temperatures of alkanols and alkanoic acids of the same chain length.
    1. What conclusion can you draw?
    2. Explains this connection.
      You can use the following key questions to help:
      • Draws two ethanol molecules and two ethanoic acid molecules.
      • Give the partial charges of the functional groups.
      • What forces of attraction exist between the ethanol molecules and between the ethanoic acid molecules?

Alternatively, the boiling temperatures of the n-alkanoic acids can also be compared with those of the n-alkanes:


work in groups


physical and chemical properties of alkanoic acids

Group 2: Solubility of alkanoic acids

Carry out the following experiments and solve the tasks in your group. You have 20 minutes for this. Enter the results on the slide. Choose a group speaker to present your results.

Attempt:

equipment

  • 8 test tubes
  • 2 measuring cylinders
  • 3 disposable pipettes
  • 1 spatula

Chemicals

  • petrol
  • water
  • Ethanoic acid (acetic acid)
  • Propanoic acid (propionic acid)
  • Pentanoic acid (valeric acid)
  • Hexadecanoic acid (palmitic acid = C 15 H 31 COOH)

Security:

Execution:
Fills 4 test tubes with approx. 5 mL dist. Water or gasoline. Use the disposable pipette or a spatula tip to add 1 mL of each alkanoic acid to a test tube filled with water or gasoline and carefully shake the test tube to mix the samples. Warm the sample with palmitic acid a little in your hand.

Tasks:

  1. Record your observations in a table.
  2. From your observation, derive a rule for the gasoline or water solubility of the alkanoic acids depending on the length of the C chain.
  3. Give the structural formulas of ethanoic acid and pentanoic acid. Marks the polar or non-polar parts of the molecule in the molecular structures.
  4. Explains the solubility behavior of alkanoic acids in water or gasoline.

work in groups


physical and chemical properties of alkanoic acids

Group 3: Conductivity of alkanoic acids

Carry out the following experiment under the fume cupboard and solve the tasks in your group. You have 20 minutes for this. Enter the results on the slide. Choose a group speaker to present your results.

Attempt:

equipment

  • 3 beakers
  • Conductivity tester

Chemicals

  • Distilled water
  • Concentrated ethanoic acid (acetic acid)


security

Execution:

  • Add 80 mL dist. Water in a beaker. Hold the conductivity tester in the dist. Water and note your observation. Carefully dry the examiner with a paper towel.
  • Your teacher now fills 20 mL of concentrated acetic acid into another beaker. Check the conductivity here too and make a note of your observation.
  • Now slowly give at least. Water to the acetic acid. Check the conductivity during the addition and note your observations during the dilution process.

Caution: After the measurement, rinse the conductivity tester thoroughly over the third beaker with distilled water. Water off and dry it gently.

Task:
Justify your observations. The following impulses can help you:

  1. What requirements does a solution have to meet in order to conduct electricity?
  2. When the acetic acid is diluted, the following reaction occurs:

    + H2O + H3O +

work in groups


physical and chemical properties of alkanoic acids

Group 4: Alkanoic acids are acidic

Carry out the following experiment and solve the tasks in your group. You have 20 minutes for this. Enter the results on the slide. Choose a group speaker to present your results.

Attempt:

equipment

  • 4 test tubes
  • Universal indicator
  • Measuring cylinder

Chemicals

  • Table vinegar
  • Lemon juice
  • yogurt
  • tap water

Execution:

  • Put approx. 1 cm of the food to be examined (with yoghurt you use the liquid supernatant) in each test tube. Add 2 drops of universal indicator to each one.
  • Observe the color of the indicator and determine the pH value with the help of the color scale. Enter your values ​​in the table (see result slide).

Tasks:

  1. What statements can you make about the food based on the pH value?
  2. Think about which three acids in the three foods are responsible for the determined pH value. Look for the right acids on the teacher's desk and put the appropriate food next to it (you can also use your chemistry book to help).
  3. For a solution to react acidic, "acidic particles", the H3O + ions, must be present in the solution.

+ H2O + H3O +

    • Name the acid in the above reaction equation and mark the particle in the acid that is responsible for the acidic reaction.
    • Explains the formation of H3O + ions in an aqueous ethanoic acid solution with the help of the reaction equation.

Summary of physical and chemical properties of alkanoic acids

Boiling temperatures of the alkanoic acids

Relationship between the boiling temperature and the carbon chain length in alkanoic acids:
________________________________________________________________________
Explanation:________________________________________________________________________________________________________________________________________
Explanation for the difference in the boiling temperature between alkanols and alkanoic acids of the same carbon chain length:
________________________________________________________________________________________________________________________________________________________________________________________________________________________

Solubility of alkanoic acids
Rule for the solubility of alkanoic acids in gasoline and water:
________________________________________________________________________________________________________________________________________________
Explanation for the solubility:
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Conductivity of the alkanoic acids
Electrical conductivity of dist. Water:______________________________________
Electrical conductivity of conc. Acetic acid:___________________________________
Electrical conductivity of the aqueous acetic acid solution: __________________________
One solution conducts electricity when ________________________________.
When the acetic acid is diluted, the following reaction occurs:

+ H2O + H3O +

Explanation for the observed electrical conductivity of the conc. Acetic acid and the aqueous acetic acid solution:
________________________________________________________________________________________________________________________________________________________________________________________________________________________

The acidic reaction

 

Table vinegar

Lemon juice

yogurt

tap water

PH value

       

contained acid

       

For a solution to react acidic, "acidic particles", the H3O + ions, must be present in the solution.
Reaction equation: see above
Explanation:
________________________________________________________________________________________________________________________________________________________________________________________________________________________

Summary - solution physical and chemical properties of alkanoic acids

Boiling temperatures of the alkanoic acids

Relationship between the boiling point and the carbon chain length in alkanoic acids:
The longer the C-chain, the higher the Sdt.
Explanation: as the chain length increases, so do the forces of attraction (here: Van der Waals forces) between the molecules.
Explanation for the difference in the boiling temperature between alkanols and alkanoic acids of the same carbon chain length:
Stronger forces of attraction exist between alkanoic acid molecules than between alkanol molecules of the same chain length (in the case of alkanoic acids, in addition to the H-bridges based on the OH groups, dipole-dipole interactions also come into play).

Solubility of alkanoic acids
Rule for the solubility of alkanoic acids in gasoline and water:
The longer the chain, the worse the alkanoic acid dissolves in water, the better it dissolves in gasoline.
Explanation for the solubility:
With increasing chain length, the influence of the lipophilic C chain increases, the influence of the hydrophilic carboxyl group decreases.

Conductivity of the alkanoic acids
Electrical conductivity of dist. Water: does not lead
Electrical conductivity of conc. Acetic acid: does not lead
Electrical conductivity of the aqueous acetic acid solution: directs
A solution conducts the electrical current, though moving charged particles are present.
When the acetic acid is diluted, the following reaction occurs:

+ H 2 O + H 3 O +

Explanation for the observed electrical conductivity of the conc. Acetic acid and the aqueous acetic acid solution:
The acid gives an H + to the water, creating a positively charged H. 3 O + Ion and a negatively charged carboxylate ion. So there are charged particles in the solution.
The acidic reaction

 

Table vinegar

Lemon juice

yogurt

tap water

PH value

approx. 2.5

approx. 2.5

approx. 3.8 -6.5

approx. 7 (6-8.5)

contained acid

acetic acid

Citric acid /
Fruit acids

Lactic acid

-

In order for a solution to react acidic, "acidic particles", the H 3 O + -Ions be present in the solution.
Reaction equation: see above

Explanation:
When an acid reacts with water, H is formed 3 O + -Ions. These are responsible for the acidic reaction.


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