Cliffs AP Chemistry, 3rd Edition

(singke) #1
(d) Pure HCl is not an acid.


  • An acid is measured by its concentration of H+(its pH).

  • Pure HCl would not ionize; the sample would remain as molecular HCl (a gas).

  • In order to ionize, a water solution of HCl is required:
    HCl(aq) →H+(aq) +Cl–(aq)


(e) HClO 4 is a stronger acid than HClO 3 , HSO 3 – , or H 2 SO 3.


  • As the number of lone oxygen atoms (those not bonded to H) increases, the strength of the
    acid increases. Thus, HClO 4 is a stronger acid than HClO 3.

  • As electronegativity of central atom increases, acid strength increases. Thus, Cl is more
    electronegative than S.

  • Loss of H+by a neutral acid molecule (H 2 SO 3 ) reduces acid strength. Thus, H 2 SO 3 is a
    stronger acid than HSO 3 –.

  • As effective nuclear charge (Zeff) on the central atom increases, acid strength is likewise
    increased. Thus, a larger nuclear charge draws the electrons closer to the nucleus and
    binds them more tightly.


Part B: Question 6


Question 6 might best be answered in the bullet format.



  1. Restatement: Interpret using bonding principles.
    (a) Restatement: Compare carbon-to-carbon bond lengths in C 2 H 2 and C 2 H 6.



  • Lewis structure of C 2 H 2 :

  • Lewis structure of C 2 H 6 :


•C 2 H 2 has a triple bond, whereas C 2 H 6 consists only of single bonds.


  • Triple bonds are shorter than single bonds since bond energy is larger for a multiple bond.
    The extra electron pairs strengthen the bond, making it more difficult to separate the
    bonded atoms from each other.


H

C

H

H

H
H C H

H C CH

Answers and Explanations for the Practice Test
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