CHAPTER 19 - 4, 7, 11, 13, 17, 25, 27, 31, 38, 40, 51, 53, 62, 71, 72, 74, 75, 78, 80, 87, 88, 90,
91
4)Buffer capacity is a measure of the ability of buffer to resist the pH changes. It depends on the
absolute and relative concentrations of the components present in the buffer. More will be the
concentration of components of a buffer; higher will be the capacity and vice-a-versa. Adding
the same amount of
or
to buffers of different capacities produces a smaller pH
change in the higher capacity buffer and larger pH change in the lower capacity buffer. A buffer
with high capacity can resist the change in pH of the solution by the addition of concentration of
acid or base to larger extent. Buffer capacity can be determined from the absolute and relative
concentrations of the components present in it. In terms of absolute concentrations, the buffer
capacity is more if the concentrations of the acid and its conjugate base present in the buffer are
high and it is less if the concentrations are low. In terms of relative concentrations, the buffer
capacity is high if the concentrations of the acid its conjugate base are equal. It decreases as the
difference in concentrations of these two species increases. Hence, the addition of 0.01 mol of
HCl produce a greater change in buffer with low capacity.
7) Acetic acid is not useful to prepare a buffer of pH 3.5. The disadvantage of using acetic acid
is, if the she uses acetic acid to prepare the buffer of pH 3.5, it will not be affective. So, she
should use formic acid to prepare the buffer of pH 3.5.The formic acid reacts with NaOH and
forms formate ion(conjugate base)
11)
a. If the given sample shows a greater number of species, that means the concentration of
that particular species is higher. As buffer 3 contains a greater number of HA molecules
that the other two, the concentration of HA in buffer 3 is higher. Therefore, buffer 3 can
react with largest amount of added strong base.
80)
a. The solubility product of strontium sulfate is
and barium chromate is
respectively. Now, compare the solubility products of each compound as
follows:The solubility product of strontium sulfate is greater than the solubility product
of barium chromate then,
strontium sulfate is more soluble in water.
b. The solubility product of calcium carbonate is
.Thus,
and copper(II) carbonate is
respectively. Now, compare the solubility products of each compound as
follows: The solubility product of calcium carbonate is greater than the solubility product
of copper (II) carbonate then,
.Thus, calcium carbonate is more soluble in water .
c. The solubility product of barium iodate is
and silver chromate is
respectively. Now, compare the solubility products of each compound as follows: The
solubility product of is barium iodate greater than the solubility product of silver
chromate then,
soluble in water.
.Thus, barium iodate is more