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12: Homework Solutions

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    43946
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    Properties of Acids and Bases

    (01) Arrhenius acid: releases hydrogen ions; Bronsted-Lowry acid: hydrogen ion donor; Bronsted-Lowry base: hydrogen ion acceptor

    (02)

    1. \(HCN + H_2O \rightleftharpoons CN^- + H_3O^+\)
    2. \(CO_3^{2-} + H_2O \rightleftharpoons HCO_3^- + OH^-\)
    3. \(NH_4^+ + H_2O \rightleftharpoons NH_3 + H_3O^+\)
    4. \(H_2SO_4 + H_2O \rightarrow HSO_4^- + H_3O^+\)
    5. \(CH_3CO_2H + H_2O \rightleftharpoons CH_3CO_2^- + H_3O^+\)

    Conjugate Acids and Bases

    (03) For each of the following acids, determine the form of their conjugate bases.

    1. SO42-
    2. HCO3-
    3. F-
    4. PO43-
    5. HCOO-

    (04) For each of the following bases, determine the form of their conjugate acids.

    1. HBr
    2. HNO3
    3. HS-
    4. NH4+
    5. H2CO3

    Strengths of Acids and Bases

    (05) strong acid: substances that fully ionize in water to create hydronium ions.

    \[HNO)3 + H_2O \rightarrow NO_3^- + H_3O+\]

    \[H_2S + H_2O \rightleftharpoons CN^- + H_3O^+\]

    (06) strong base: substance that fully ionize to produce hydroxide ions in water

    \[LiOH + H_2O \rightarrow H_2O + Li^+ + OH^- \]

    which simplifies to

    \[LiOH \rightarrow Li^+_{(aq)} + OH^-_{(aq)}\]

    (07)

    H3PO4 + H2O \(\rightleftharpoons\) H2PO4- + H3O+

    H2PO4- + H2O \(\rightleftharpoons\) HPO42- + H3O+

    HPO42- + H2O \(\rightleftharpoons\) PO43- + H3O+

    (08) For each chemical reaction, determine whether they are representative of the dissociation reaction of a strong acid, a weak acid, a strong base, or a weak base.

    1. strong base
    2. ​weak acid
    3. weak base
    4. weak acid
    5. strong acid

    (09)

    1. HClO4\(\rightleftharpoons\) H+ + ClO
    2. HSCN \(\rightleftharpoons\) H+ + SCN-
    3. HBr → H+ + Br-
    4. H2CO3 \(\rightleftharpoons\) H+ + HCO3-
    5. CH3COOH \(\rightleftharpoons\) H+ + CH3COO​-

    (10)

    ch12q10answer.png

    Acid-Base Equilibria

    (11) equilibrium: a state in which the forward and reverse reactions are occurring at the same rate

    H2O \(\rightleftharpoons\) OH- + H+

    No, the concentrations of the reactants and products remain constant when a reaction is at equilibrium.

    The double arrow represent the forward and reverse reactions occurring simultaneously.

    Le Chatelier’s Principle

    (12)

    1. left
    2. right
    3. right
    4. left

    (13)

    1. left
    2. left
    3. left
    4. right
    5. right

    (14)

    1. ​The hydrogen ion concentration increases.
    2. ​The hydrogen ion concentration decreases.

    Acid-Base Neutralization Reactions

    (15) Write out the neutralization reactions for the following pairs. Make sure to balance the equations as necessary and include phases.

    1. \(Ba(OH)_2\) + \(2HNO_3\) → Ba(NO3)2 + 2 H2O
    2. \(Ca(OH)_2\) + \(H_2SO_4\) → CaSO4 + 2 H2O
    3. \(RbOH\) + \(HI\) → RbI + H2O
    4. \(KOH\) + \(HClO_4\) → KClO4 + H2O
    5. \(Mg(OH)_2\) + 2 \(HBr\) → MgBr2 + 2 H2O

    pH

    (16) Examine the following pH measures and tell whether they are in the range to be considered acidic, basic or neutral.

    1. neutral (very slightly acidic)
    2. basic
    3. acidic
    4. acidic
    5. basic

    (17) Using the formula for converting concentration into pH, determine whether each of the following molarities are acidic, basic or neutral. Remember, -log[H+]

    1. 7.0 neutral
    2. 11.3 basic
    3. 3.2 acidic
    4. 9.1 basic
    5. 1.0 acidic

    (18) Fill in the blank portions of the table.

    \([H_3O^+]\)

    \([OH^-]\)

    \(pH\)

    Acidic, Basic or Neutral

    \(1.0 \times 10^{-1}\)

    \(1.0 \times 10^{-13}\)

    1

    acidic

    \(1.0 \times 10^{-10}\)

    \(1.0 \times 10^{-4}\)

    10

    basic

    \(1.0 \times 10^{-7}\)

    \(1.0 \times 10^{-7}\)

    7

    neutral

    \(1.0 \times 10^{-5}\)

    \(1.0 \times 10^{-9}\)

    5

    acidic

    \(1.0 \times 10^{-13}\)

    \(1.0 \times 10^{-1}\)

    13

    basic

    (19) Given the following sets of information, calculate the requested quantities for each problem.

    1. pH = 3.4 and [OH-] = 2.4 x 10-11M
    2. pOH = 8.2 and [H3O+] = 1.5 x 10-6M
    3. [H3O+] = 1.0 x 10-9M, [OH-] = 1.0 x 10-5M and pOH = 5
    4. [OH-] = 3.2 x 10-13M and [H3O+] = 3.2 x 10-2M
    5. [H3O+] = 1 x 10-7M, [OH-] = 1 x 10-7M and pH = 7

    Buffers

    (20) Buffer (buffer system): a combination of a weak acid and weak base (often conjugate acid/base pairs) at similar concentrations used to maintain constant pH

    1. no
    2. yes
    3. no
    4. yes
    5. no

    (21)

    1. HBr + HCO3- \(\rightleftharpoons\) H2CO3 + Br-
    2. LiOH + H2CO3 →​ HCO3- ​ + H2O + Li+
    3. NH4+ + HCO3- \(\rightleftharpoons\) H2CO3 + NH3
    4. HCOO- + H2CO3 \(\rightleftharpoons\) HCOOH + HCO3-
    5. CH3NH2+ H2CO3 \(\rightleftharpoons\) CH3NH3+​ + HCO3-

    (22) CO2 levels increase in the body raising the concentration of hydrogen ions and lowering the pH.


    12: Homework Solutions is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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