energy, ∆G, can be determined for a given reaction with the equation ∆G = ∆H – T∆S. Reactions
with a negative change in Gibbs free energy are spontaneous.
18 . C
Specific heat is the amount of heat required to raise the temperature of one unit mass of a
substance one degree Celsius.
19 . B
The heat of formation is the heat absorbed or released during the formation of a pure
substance from its elements at constant pressure.
20 . A
NaOH completely dissociates in water to form Na+ and OH– ions, the latter of which is a very
strong base. This results in a solution with a very high pH (>7).
21 . D
CH 3 COOH does not completely dissociate in water. There would be some undissociated
CH 3 COOH and some CH 3 COO– + H+; therefore, it would be a weak acid with a pH slightly less
than 7.
22 . C
HBr completely dissociates into Br– and H+ in water; this solution would have a very low pH
(<7).
23 . B
CsCl is a salt; it completely dissociates in water into Cs+ and Cl–. This will form an ionic solution
with a neutral pH.
25. Part B
101 . T, F
Diamond and graphite are different carbon compounds with different properties because of
different bond structures. They are allotropes, not isotopes, of one another. Diamond has a
covalent crystal structure (lattice positions occupied by atoms with covalent bonds) while in
graphite, the carbon molecules are in parallel sheets.
