Chemistry Chapter 8: Acid-Base Titrations
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Questions and Answers

What is the pH of a strong acid before a titration begins?

  • Variable depending on the concentration
  • Less than 7 (correct)
  • Greater than 7
  • Equal to 7

    • In the reaction HCl + NaOH, what is the net ionic equation?

  • HCl + Na+ → H+ + NaOH
  • NaOH + HCl → NaCl + H2O
  • H+ + OH- → H2O (correct)
  • Na+ + Cl- → NaCl

    • What is the stoichiometric ratio in the neutralization reaction of HCl and NaOH?

  • 2:1
  • 1:2
  • 1:1 (correct)
  • 1:0

    • If a strong acid is titrated with a strong base, at what point can you expect the pH to start increasing markedly?

    <p>At the equivalence point (D)</p> Signup and view all the answers

    What ions are produced when HCl reacts with NaOH?

    <p>H2O and Na+ (C)</p> Signup and view all the answers

    What is a key characteristic of titrating a strong acid with a weak base compared to a strong acid with a strong base?

    <p>The endpoint pH will be significantly higher for a strong acid and weak base titration. (A)</p> Signup and view all the answers

    Which statement accurately describes the titration of a strong base with a weak acid?

    <p>The titration results in a sharp rise in pH at the equivalence point. (B)</p> Signup and view all the answers

    When titrating a strong base against a weak polyprotic acid, what outcome can be expected?

    <p>The titration curve will show multiple inflection points corresponding to each dissociation step. (B)</p> Signup and view all the answers

    During an amino acid titration, at what point does the amino acid typically behave as a zwitterion?

    <p>At the isoelectric point where the net charge is zero. (D)</p> Signup and view all the answers

    What distinguishes the titration of a strong acid against a weak polyprotic base from other titrations?

    <p>The pH will exhibit multiple plateau regions as each functional group reacts. (D)</p> Signup and view all the answers

    Flashcards

    Neutralization Reaction

    A chemical reaction where an acid and a base react to form salt and water.

    Stoichiometric Ratio

    The ratio of moles of acid to moles of base required to neutralize each other in a reaction.

    Equivalence Point

    The point in a titration where the acid and base have completely neutralized each other.

    Titration Curve

    A graphical representation of pH changes during a titration.

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    Initial pH

    The pH of a solution before any titrant is added.

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    Strong Acid vs Strong Base Titration

    A titration where both the acid and base are strong electrolytes, resulting in a neutral pH at the equivalence point.

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    Strong Acid vs Weak Base Titration

    A titration where a strong acid reacts with a weak base. The equivalence point will be slightly acidic due to the hydrolysis of the conjugate acid of the weak base.

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    Strong Base vs Weak Acid Titration

    A titration where a strong base reacts with a weak acid. The equivalence point will be slightly basic due to the hydrolysis of the conjugate base of the weak acid.

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    Strong Acid vs Weak Polyprotic Base Titration

    A titration where a strong acid reacts with a weak polyprotic base. The titration curve will have multiple equivalence points, corresponding to the sequential deprotonation of the polyprotic base.

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    Strong Base vs Weak Polyprotic Acid Titration

    A titration where a strong base reacts with a weak polyprotic acid. The titration curve will also have multiple equivalence points, corresponding to the sequential deprotonation of the polyprotic acid.

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    Study Notes

    Chapter 8: Acid-Base Titrations

    • Acid-base titrations involve using a solution of known concentration (titrant) to determine the concentration of an unknown solution (analyte or API).
    • The reaction that occurs is a neutralization reaction.
    • Acidimetry: Quantitative determination of basic drugs
    • Alkalimetry: Quantitative determination of acidic drugs

    Titration Curves for Strong Acids and Bases

    • Strong acids and bases completely dissociate in water (e.g., HCl, HClO4, NaOH, KOH).
    • Consider only one equilibrium: Kw = [H3O+][OH-]
    • Know the stoichiometric ratio of the acid-base reaction (S.R.).
    • Example: HCl + NaOH → HOH + Na+ + Cl- S.R. = 1:1

    pH Before Titration Begins

    • Calculate the pH of a solution of a known concentration before a titration
    • Example: 100.0 mL of 0.1000 M HCl. [H3O+] = 1.000 x 10-¹M. pH = 1.0000; POH = 13.0000

    pH at Equivalence Point

    • The pH at the equivalence point in a strong acid-strong base titration is 7.0000.
    • Autodissociation of water governs the pH at the equivalence point.
    • Example: HO-H + HO-H ←→ H3O⁺ + OH⁻; Kw = [H3O⁺][OH⁻] = 10⁻¹⁴

    pH After Equivalence Point

    • Calculate the concentration of excess base(OH–) to determine pH after equivalence point
    • Calculate [OH−] using the formula: [OH−] = (Cbase Vbase − Cacid Vacid)/(Vbase + Vacid)

    Acid-Base Color Indicators

    • Indicators are organic weak acids or bases that display distinct color changes.
    • The indicator's acid and conjugate base forms have distinctly different colors, helping track the reaction progress.
    • Example: HIn + OH⁻ ⇌ In− + HOH Note: The ratio [HIn]/[In⁻] determines the solution's color

    Titration of Weak Acid and Strong Base

    • Initial point and buffer region calculations
    • midpoint pH = pKa
    • Equivalence point calculations for titration of a weak acid(HA) with a strong base(OH).

    Titration of Weak Base and Strong Acid

    • The equivalence point for a weak base and strong acid titration occurs at a pH less than 7.
    • The salt formed is acidic.

    Polyfunctional Acids/Bases Equilibria

    • Polyfunctional acids dissociate in multiple steps, each with a specific acid dissociation constant (Ka).
    • The given example uses phosphoric acid, H3PO4 (Ka1, Ka2, Ka3)
    • Calculations of pH are distinct for each step.
    • Examples: H2S + HOH → H3O⁺ + HS⁻; HS⁻ + HOH → H3O⁺ + S²⁻

    Titrations of polyprotic amino acids

    • Amino acids are polyprotic – they have multiple ionization steps.
    • calculations of their pH
    • Calculation of isoelectric point.

    Direct/Indirect Titrations

    • direct titrations,

    • residual titrations (or back titrations)

    • example calculations for each using appropriate formulas.

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    Related Documents

    Acid-Base Titrations Chapter 8 PDF

    Description

    This quiz covers the essential concepts of acid-base titrations, focusing on how to determine concentrations using titrants. It includes an exploration of titration curves for strong acids and bases, calculating pH before titration, and understanding the pH at the equivalence point. Test your knowledge on the principles of neutralization reactions and stoichiometric ratios.

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