Chemistry Chapter: Alcohols and Carboxylic Acids
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Questions and Answers

What is the correct formula for calculating concentration using the number of moles?

  • c = n × V
  • c = n / V (correct)
  • c = V / n
  • c = n + V

    • When calculating the concentration of an unknown substance, which variable represents the volume in the concentration formula?

  • m
  • n
  • c
  • V (correct)

    • In the reaction between dichromate and iron (II) ions, how many moles of Fe2+ ions react with one mole of dichromate ions?

  • 3
  • 6 (correct)
  • 1
  • 14

    • If a sample contains 12.0% (w/v) dichromate, what does this mean in terms of grams of dichromate per 100 mL of solution?

    <p>12.0 g</p> Signup and view all the answers

    After using a 32.0 mL sample of dichromate in the reaction, what is the next step to find the concentration of iron (II)?

    <p>Calculate the moles of dichromate and use stoichiometry to find moles of iron.</p> Signup and view all the answers

    What will happen to a polar object in a non-polar stationary phase?

    <p>It will have a longer retention time.</p> Signup and view all the answers

    In high performance liquid chromatography (HPLC), which of the following is true about the solvent used?

    <p>It can be non-polar for certain applications.</p> Signup and view all the answers

    How does the attraction to the stationary phase affect the rate of travel of an object?

    <p>Higher attraction results in less travel.</p> Signup and view all the answers

    What is the main advantage of using high performance liquid chromatography over traditional column chromatography?

    <p>It uses higher pressures, speeding up the process.</p> Signup and view all the answers

    If component A has the shortest retention time in a non-polar solvent system, what can be inferred about its nature?

    <p>It is non-polar and travels quickly through the column.</p> Signup and view all the answers

    Why would an object be desorbed from the stationary phase?

    <p>It is more attracted to the mobile phase.</p> Signup and view all the answers

    What does a longer retention time indicate regarding an object's interaction with the stationary phase?

    <p>The object is strongly adsorbed.</p> Signup and view all the answers

    During the process of adsorption, what factor primarily determines the speed at which an object travels through a chromatography column?

    <p>The object's interaction with the mobile phase.</p> Signup and view all the answers

    What does the term 'aliquot' refer to in the context of chemical analysis?

    <p>A sample taken from a larger whole for analysis</p> Signup and view all the answers

    How is the number of moles of a primary standard calculated?

    <p>By using the formula $n = M.r$</p> Signup and view all the answers

    In a titration setup, where is the 'titre' located?

    <p>In the burette above</p> Signup and view all the answers

    What is the correct formula for calculating concentration?

    <p>c = \frac{n}{v.Aliquot}</p> Signup and view all the answers

    Which of the following is a key strategy for solving volumetric analysis problems?

    <p>Drawing a diagram of the titration setup</p> Signup and view all the answers

    What observable effect indicates that an esterification reaction has occurred when adding an alcohol?

    <p>Production of a fruity smell</p> Signup and view all the answers

    What is produced when ethanoic acid reacts with sodium carbonate?

    <p>Sodium ethanoate, carbon dioxide, and water</p> Signup and view all the answers

    If no bubbles are observed when adding sodium hydrogen carbonate to a substance, what can be inferred about the substance?

    <p>The substance is not an acid</p> Signup and view all the answers

    Which of the following tests is used to check for the presence of a hydroxyl group in alcohols?

    <p>Bromine/Iodine Test</p> Signup and view all the answers

    When adding an acid to test for the carboxyl group, what happens that indicates a positive reaction?

    <p>Gas bubbles form</p> Signup and view all the answers

    Which reagent can be used to produce a fruity smell indicative of an ester?

    <p>Alcohol</p> Signup and view all the answers

    What does the formation of bubbles when testing a substance with sodium carbonate suggest?

    <p>The substance is a weak acid</p> Signup and view all the answers

    What type of functional group must be present for the esterification reaction involving alcohols?

    <p>Carboxyl Group</p> Signup and view all the answers

    How does the purity of a substance affect its melting point behavior?

    <p>Pure substances melt at roughly the same temperature</p> Signup and view all the answers

    In the context of testing for alcohol, which reagent is appropriate in the Hydroxyl Group Test?

    <p>Potassium dichromate</p> Signup and view all the answers

    What is the mean titre calculated from the given titres?

    <p>17.29 mL</p> Signup and view all the answers

    How many concordant titres were identified from the data provided?

    <p>3</p> Signup and view all the answers

    Using the mean titre, what is the expression for the number of moles of potassium dichromate used?

    <p>$n(K_2Cr_2O_7) = cV$ where $c = 1.62 \times 10^{-3} \text{mol/mL}$</p> Signup and view all the answers

    What is the result of the calculation for moles of potassium dichromate used, given the mean titre?

    <p>2.800 × 10^{-5} mol</p> Signup and view all the answers

    Which of the following correctly defines the concentration of a solution?

    <p>The number of moles of solute per volume of solution in liters</p> Signup and view all the answers

    If the concentration of potassium dichromate is 1.62 × 10^{-3} mol/100 mL, what is this concentration in mol/L?

    <p>0.0162 mol/L</p> Signup and view all the answers

    Which volume was not recognized as a concordant titre?

    <p>17.40 mL</p> Signup and view all the answers

    Why is identifying concordant titres important in titration?

    <p>It ensures consistency of results.</p> Signup and view all the answers

    Study Notes

    Alcohol and Carboxylic Acids

    • An indication of an esterification reaction: addition of alcohol results in the formation of fruity-smelling esters.
    • Ethanoic acid (CH₃COOH) reacts with sodium carbonate to produce sodium ethanoate, carbon dioxide, and water.
    • Reaction: 2CH₃COOH(aq) + Na₂CO₃(s) → (CH₃COO)₂Na(aq) + CO₂(g) + H₂O(l).
    • Ethanoic acid also reacts with sodium hydrogen carbonate, yielding sodium ethanoate, carbon dioxide, and water.
    • Reaction: CH₃COOH(aq) + NaHCO₃(s) → CH₃COONa(aq) + CO₂(g) + H₂O(l).
    • Observations indicate an acid presence if bubbles of CO₂ form; lack of bubbles suggests it is not an acid.

    Chemical Tests for Functional Groups

    • Tests for double bonds (C=C): Bromine/Iodine test, adding H⁺ (aq)/MnO₄⁻ (aq) or H⁺ (aq)/Cr₂O₇²⁻ (aq) reacts with primary or secondary alcohols.
    • Hydroxyl Group: Addition of a reagent forms a smelly ester to confirm the presence of an alcohol.
    • Carboxyl Group: Adding a carbonate reagent leads to the evolution of bubbles, indicating acidic properties.

    Purity Analysis & Concentration

    • A pure substance melts at a consistent temperature; impurities lead to varied melting points.
    • In chromatography, the interaction depends on polarity: non-polar substances move slower on polar stationary phases.
    • High-Performance Liquid Chromatography (HPLC) enhances efficiency with high pressures in separating components from mixtures.

    Stoichiometric Calculations

    • Concentration (c) is calculated as n/V, where n is moles and V is volume.
    • A non-polar solvent in HPLC separates components based on their retention times.
    • When calculating the concentration of dichromate involving multiple components, foundational concentration formulas are applied:
      • n = m/M (for moles from mass).
      • c = n/V (for concentration).

    Titration

    • In titration procedures, titre refers to the solution in the burette, and aliquot refers to the sample in the flask.
    • To find the mean titre, calculate the average from concordant titres.
    • Moles of potassium dichromate are derived from concentration and volume.
    • Final concentration calculations can apply to specific body analyses, such as ethanol concentration expressed in mol/100 mL.

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    Description

    This quiz covers the reactions and tests involving alcohols and carboxylic acids, particularly focusing on esterification and identification of functional groups. Understand the reaction mechanisms and the observations that indicate the presence of specific compounds through various chemical tests.

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