(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.
- 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