The trick is understanding what should happen to each when it is dissolved in water. Choice D,
potassium cyanide, in addition to being highly poisonous, is the salt of a strong base, KOH, and
a weak acid, HCN. When the salt dissolves in water, the potassium ion does not react with
water, but the cyanide ion picks up hydrogen ions from the water to establish an equilibrium
with hydrocyanic acid. The result is that excess hydroxide ions are created, and the solution is
basic.30 . D
Avogadro’s number, 6.02 × 10^23 , is the number of molecules in one gram molecular weight of a
substance, or one mole of the substance. So the correct answer choice is the one that does not
describe one mole of a species. You probably remember that a mole of gas at STP occupies a
volume of 22.4 liters. Choice A gives the volume of a half mole of oxygen molecules, but since
each molecule of oxygen gas has two oxygen atoms, choice A represents Avogadro’s number
of atoms. Choice B, one mole of helium, is a mole. Choice C is the definition of a Faraday,
which is one mole of electrons. Choice D, the number of sulfate ions in a 0.5 M sulfuric acid
solution, is not a mole. The reason is that there are two equivalents of hydrogen in each mole
of sulfuric acid. A 0.5 M solution contains one mole of hydrogen ions, but only a half mole of
sulfate ions. One mole of sulfate ions from sulfuric acid would have to be 2 N.
31 . C
A state function is one whose value depends only on the initial and final states of the system; it
is independent of the path taken in going from the initial to the final states. Examples of state
functions are pressure, volume, temperature, density, viscosity, enthalpy, internal energy,
entropy, and free energy. Two import functions that are not state functions are work and q,
the amount of heat transferred.
32 . B
33 . A
The question asks you to give the range of possible values for the ratio of hydroxide ion
concentration to hydrogen ion concentration in an aqueous acid solution. For a solution to be
acidic, it must have a pH between about 1 and 6.9999. This means that the pOH of these
solutions will be between 13 and 7.0001. We know that pH is equal to the negative log of the