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    Organic Chemistry - Calculating Molar Solubility

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    6. Calculate the molar solubility of Mg(OII)_2 in a solution with a pH of 12.8 (K_op of Mg(OH)^2 is 1.2 * 10^-11

    7. For a reaction to be spontaneous at any temperature, which one of the following is true:
    a) [delta] H is positive and [delta] S is positive
    b) [delta] H is positive and [delta] S is negative
    c) [delta] H is negative and [delta] S is negative

    8. Which one of the following solutions can act as a buffer?
    a) Nat/HI
    b) NaOH/NaCI
    c) NaCN/HCN
    d) NAI/CH_3COONa

    9. A student is asked to prepare a buffer solution at pH = 3.6, which one of the following weak acids should be used?
    a) NH_4CI (K_b = 1.8 * 10^-5 for NH_4OH
    b) HA (K_a = 2.7 * 10 ^-4)
    c) HB (K_a = 1.5 * 10^-9)
    d) HC (K_a = 5.3 * 10^-13)

    10. Which one of the following statements is false?
    In the equilibrium Mg(OH)_ (s) ---Mg^2+ (aq) + 2OH(aq)
    a) The reaction moves forward when adding in acid
    b) The reaction moves backward when adding in solid NaCl
    c) The reaction moves backward when adding in solid MgCl^2
    d) The reaction moves forward when adding in water

    11. Acetic acid, CH_3COOH is a weak acid (K_a - 1.8 * 10 ^-5)
    a) Solution A is 100ml of 0.10M acetic acid
    b) Solution B is prepared by adding 0.0050 mol solid NaOH to Solution A
    c) Solution C is prepared by adding 0.010 mol solid NaOH to Solution A
    d) Solution D is made by adding 0.0150 mil solid NaOH into Solution A
    e) Calculate the pH for each of the solutions, A,B,C, and D

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    https://brainmass.com/chemistry/organic-reactions/organic-chemistry-calculating-molar-solubility-533838

    Solution Preview

    6. Mg(OH)2 -> Mg2+ + 2OH-
    As pH = 12.8, pOH = 1.2 which means [OH-] = 10-1.2 = 0.063 M
    If 's' is the molar solubility,
    Ksp = (s)(2s + 0.063)2 = 1.2 x 10-11
    As molar solubility will be really small compared to 0.063, hence 2s + 0.063 = 0.063 approximately
    Hence, s(0.063)2 = 1.2 x 10-11
    Solving for molar solubility, s = 3 x 10-9 M

    7. [delta] G = [delta] H - T[delta] S
    For spontaneity, [delta] G must be negative. This is possible at all T if [delta] H is negative and ...

    Solution Summary

    The molar solubility is calculated for organic chemistry. The expert determines if the reaction is spontaneous at any temperature.

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