temperature never enters into the calculations.
- B Since these are all ionic compounds, electrostatic forces can be assumed
to be entirely responsible for the cohesive forces on the lattice. According
to Coulomb’s law
F = Kq 1 q 2 /r^2 where Energy = Kq 1 q 2 /r
Since the charges for all of the ion pairs given in the choices
(q 1 and q 2 ) are ±1, it is the internuclear distance, r, of each
ion pair that is the determinant factor. According to the
equations above, the smaller the r, the greater the energy. So
using the periodic trend in atomic/ion size, LiF (choice (B))
is the ion pair with the smallest internuclear distance.
- C Positron emission is a type of beta decay. During beta decay, nuclear
mass remains constant. Therefore, choice (C) is the only possible answer.
Conserving mass (superscript) and charge (subscript) gives
choice (C).
- E A reducing agent describes a species that will lose electrons easily in a
redox reaction. This in turn causes another species to gain electrons and
thus be reduced. Out of the choices, sodium loses its one valence electron
to form Na+ ions very readily. This also means that sodium would be very
high on the activity series.
- C Recall the solubility rules. (A) and (B) are incorrect because neither
NaCl nor BaOH are insoluble and therefore would not precipitate out of
the aqueous solution. Because lead salts are insoluble except for their
nitrates and perchlorates, lead iodide would precipitate out of solution as
(C) depicts. Answer choices (D) and (E) are examples of oxidation-
reduction reactions.
- A Cell diagrams are read as
