EXTRA REVIEW 2A
1. A solution is prepared by mixing 80.0 mL of a 0.50 M nitrous acid solution and 20.0 mL of a 0.25 M
sodium nitrite solution. Will this be a buffer solution? Calculate the pH. Is this solution acidic or
basic?
2. A solution is prepared by mixing 80.0 mL of a 0.50 M nitrous acid solution and 20.0 mL of a 0.25 M
sodium hydroxide solution. Will this be a buffer solution? Calculate the pH. Is this solution acidic or
basic?
3. A solution is prepared by mixing 50.0 mL of a 0.45 M pyridine (C5H5N) solution and 25.0 mL of a
0.60 M pyridine hydrochloride (C5H5NH+Cl-) solution. Will this be a buffer solution? Calculate the
pH. Is this solution acidic or basic?
4. A solution is prepared by mixing 50.0 mL of a 0.45 M pyridine solution and 50.0 mL of a 0.60 M
hydrochloric acid solution. Will this be a buffer solution? Calculate the pH. What will be the
concentration of the chloride ions in the solution?
5. A solution is prepared by mixing 50.0 mL of a 0.45 M pyridine solution and 25.0 mL of a 0.60 M
hydrochloric acid solution. Will this be a buffer solution? Calculate the pH. Is this solution acidic or
basic?
6. From the data given in Handout 1 on the class website, determine the best weak acid – conjugate base
pair to prepare a buffer of pH = 9.00.
7. Calculate the molar ratio of base to conjugate acid in a solution that has a pH of 10.25 and contains the
base ethylamine (C2H5NH2) and a salt of its conjugate acid, ethylamine hydrochloride (C2H5NH3+Cl-).
*8. Determine the volumes of 1.0 M NaX, 1.0 M HCl, and water needed to produce 100.0 mL of a buffer
that is 0.20 M HX and 0.30 M NaX.
*9. Determine the volume of 1.0 M NaOH that must be mixed with 50.0 mL of 0.20 M HX to produce a
buffer with pH = 6.
EXTRA REVIEW 2B
1. A solution is 0.45 M in cyanic acid (HOCN) and 0.20 M in sodium cyanate (NaOCN). The Ka for
cyanic acid is 3.5 x 10-4.
(a) Calculate the pH of the solution. Is the solution acidic or basic?
(b) Calculate the final pH if 0.10 gram of sodium hydroxide is added to 1.00 liter of the buffer
solution, assuming ther volume does not change.
(c) Calculate the final pH if 0.50 gram of sodium hydroxide is added to1.00 liter of the buffer instead
of 0.10 gram, still assuming the volume does not change.
2. A buffer is prepared by mixing 30. mL of a 1.5 M hydrofluoric acid solution with 20. mL of a 2.0 M
sodium fluoride solution.
(a) Calculate the pH of the solution. Is the solution acidic or basic?
(b) Calculate the final pH if 5 mL of a 1.0 M hydrochloric acid solution is added to the buffer.
(c) Calculate the final pH if 5.0 mL of a 1.0 M sodium hydroxide solution is added to the buffer
solution instread of the hydrochloric acid solution.
EXTRA REVIEW 2C
1. Hydrazine (N2H4) is a weak organic base that reacts with water as follows:
N2H4 + H2O ⇄ N2H5+ + OHThe base dissociation constant for this reaction, Kb = 1.7 x 10-6. When titrated with hydrochloric acid,
hydrazine reacts as follows:
N2H4 + HCl → N2H5+ + Cl(a) 50.0 mL of a 0.100 M solution of hydrazine are titrated with 0.250 M hydrochloric acid. Calculate
the volume of the hydrochloric acid solution required to neutralize the hydrazine.
(b) Calculate the pH of the hydrazine solution at the beginning of the titration.
(c) Calculate the pH of the resulting solution after 5.00 mL of the hydrochloric acid solution has been
added.
(d) Calculate the pH of the resulting solution after 10.00 mL of the hydrochloric acid solution has
been added.
(e) Calculate the pH of the resulting solution at the equivalence point.
(f) Calculate the pH of the resulting solution after 25.00 mL of the hydrochloric acid solution has
been added.
(g) Sketch the titration curve for the titration of 0.100 M hydrazine with 0.250 M hydrochloric acid.
Plot accurately the pH at the beginning of the titration, and after the addition of 5.00 mL, 10.00
mL, 20.00 mL, and 25.0 mL of the 0.250 M hydrochloric aicd.
(h) From the list of indicators in Figure 15.8, what would be the best indicator for this titration?
(continued on next page)
2. The titration curve for a weak diprotic acid, H2X, being titrated with a strong base is shown. Indicate
the following.
(a) The point on the titration curve when the
solution contains only H2X
(b) The point on the titration curve when the
solution contains equal amounts of H2X and HX(c) The point on the titration curve when the
solution contains only HX(d) The point on the titration curve when the
solution contains equal amounts of HX- and X2(e) The point on the titration curve when the
solution contains only X2(f) The Ka1 of the weak diprotic acid and the Ka2 of
the weak diprotic acid
(g) From Table 15.8 in the textbook, determine the best indicator to use in order to signal the first
equivalence point for this titration
(h) From Table 15.8 in the textbook, determine the best indicator to use in order to signal the second
equivalence point for this titration
*3. For a titration between 10.0 mL of 0.20 M HX and 0.10 M NaOH:
(a) Determine the mL of the NaOH solution needed to reach the equivalence point
(b) Determine the pH of the 0.20 M HX solution before the titration
(c) Determine the pH of the solution after the addition of 5.0 mL of NaOH
(d) Determine the pH of the solution after the addition of 10.0 mL of NaOH
(e) Determine the pH of the solution after the addition of 15.0 mL of NaOH
(f) Determine the pH of the solution after the addition of 20.0 mL of NaOH
(g) Determine the pH of the solution after the addition of 25.0 mL of NaOH
(h) Determine the acid ionization constant for HX
(i) Determine the best indicator for this titration from the indicators in Table 15.8
*4. A student titrated a spoonful of an unknown monoprotic acid with an NaOH solution of unknown
concentration. After adding 5.00 mL of base, he found the pH of the solution to be 6.0. The
equivalence point came when 7.00 mL of additional base was added. Calculate the ionization constant
of the acid.
*5. Clinicians are frequently required to determine the bicarbonate concentration in human blood since the
HCO3- concentration, along with that of dissolved CO2, affects the pH of the blood. The HCO3concentration is easily determined by titimetry employing an excess of HCl, which is back-titrated
with NaOH. Write equations for the two reactions, and calculate the HCO3- concentration in a 0.10
mL serum sample that requires addition of 1.00 mL of 0.010 M HCl followed by back-titrating with
0.76 mL of 0.010 M NaOH.
EXTRA REVIEW 2D
1. The solubility of tin (II) fluoride in water is 0.049 grams per liter at 20ºC. Calculate the solubility
product, Ksp, for this salt at 20ºC.
2. Look up the solubility product constants for silver hydroxide, manganese (II) hydroxide, and
chromium (III) hydroxide, and determine which salt is most soluble in water.
3. Using data from Handout 2 on the class website:
(a) Calculate the solubility of cobalt (II) sulfide, in moles per liter and grams per liter, in pure water
at 25ºC.
(b) Calculate the solubility of cobalt (II) sulfide, in moles per liter and grams per liter, in a solution
that is 0.10 M Na2S at 25ºC.
4. A solution is made 0.10 M in Ba(NO3)2, and 0.05 M in NaF. Will BaF2 precipitate?
*5. At 20ºC, the solubility product, Ksp, for cadmium phosphate is 2.5 x 10-33.
(a) Calculate the cadmium ion concentration in a solution of cadmium phosphate in pure water at
20ºC.
(b) Calculate the cadmium ion concentration in a 0.10 M phosphate ion solution at 20ºC.
*6. At 20ºC, the solubility product, Ksp, for silver chromate is 1.9 x 10-12.
(a) Calculate the silver ion concentration in a solution of silver chromate in pure water at 20ºC.
(b) Calculate the silver ion concentration in a 0.10 M chromate ion solution at 20ºC.
EXTRA REVIEW 2E
1. Calculate the concentration of nickel (II) ions needed to precipitate nickel (II) hydroxide in a buffer
solution of pH 12.00.
2. A solution is made 0.30 M in Ca2+, and NaOH is added until the OH- concentration is 0.0050 M.
Calculate the percentage of Ca2+ ions left in the solution at this point.
3. Phosphate ions are slowly added to a solution containing 0.100 M calcium ions and 0.200 M silver
ions.
(a) What cation will be the first to precipitate?
(b) What will be the concentration of the phosphate ions when the first cation starts to precipitate?
(c) What will be the concentration of the first cation when the second cation starts to precipitate?
4. In the precipitation of metal sulfides, selective precipitation can be achieved by adjusting the hydrogen
ion concentration. Calculate the pH that CoS begins to precipitate from a water solution saturated with
H2S (0.077 M) and containing 0.08 M Co2+.
5. Calculate the solubility of ZnS at pH 10.00 and at pH 0.00 in a water solution saturated with H2S
(0.077 M).
*6. A solution is made 0.10 M in Mg2+, 0.10 M in NH3, and 1.0 M in NH4Cl. Will Mg(OH)2 precipitate?
*7. Calculate the solubility of Mg(OH)2 at pH 2.0 and at pH 12.0 in a water solution.
EXTRA REVIEW 2F
1. Find the Chart of the Nuclides on the internet at the web site for the National Nuclear Data Center,
and complete the following data for data concerning all known isotopes of neon.
Isotope
Stable or Radioactive
Natural Abundance
Half-Life
2. Complete the following nuclear equations and supply symbols of values for X or x.
(a)
19
(b)
176
(c)
X
XC

(d)
X
XS
+
0
(e)
26
XMg
+
(f)
16
9X
XLu
8X
1
+
+
xH

X
11
1
8X
+
+
X
-
+1β
4
XX
+
30
15X


-1β
0
+

0n
1X
16
XX
XX
-1e
2

4
14
Xα
7X
X
+
+
XX
4
XX
3. Write equations for each of the following nuclear processes.
(a) beta positive decay by 7032Ge
(b) beta minus decay by 8035Br
(c) alpha decay by 22387Fr
(d) electron capture by 2614Si
4. What type of decay would you expect from each of the following radioisotopes?
(a) 3H
(b)
105
Ag
(c)
236
U
Decay Mode
EXTRA REVIEW 2G
1. Radioactive 123I, which as a half-life of 13.2 hours is used for diagnostic study of thyroid diseases.
How many days will it take for the radioactivity to fall to 5.00% of its original intensity?
2. If 1.000 g of 60Co decays by β- emission to 0.063 g in 21 years, what is the half-life of 60Co?
3. A sample of a radioisotope shows an activity of 161. disintegrations per minute. After 45.0 minutes,
the activity decreases to 53 disintegrations per minute. Determine the half-life of the radioisotope.
4. In the skeleton of a fish caught in French Polynesia in 2005, the 14C disintegration rate was 17.2 cpm
g-1 of carbon. Calculate the age of the fish. How can this be? What does this imply about South Pacific
archaeology?
5. In a sample of zircon from the Jack Hills of Western Australia, the mass of Pb is 84.4% the mass of
the U present. Estimate a minimum age for the earth from this information.
6. Calculate the binding energy per nucleon for the following nuclear species.
(a)
32
16S
(m = 31.97207 u)
(b)
16
8O
(m = 15.99491 u)
*7. The half-lives of 235U and 238U are 7.1 x 108 years and 4.5 x 109 years respectively. Presently, uranium
is 99.28% 238U and 0.72% 235U. Calculate the percent natural abundance of each uranium isotope
when the earth was formed 4.5 billion years ago.
*8. The half-lives of 235U and 238U are 7.1 x 108 years and 4.5 x 109 years respectively. Presently, uranium
is 99.28% 238U and 0.72% 235U. Calculate the percent natural abundance of each uranium isotope in
1.0 billion years from now.
EXTRA 2A ANSWERS
1. yes, 2.49, acidic
2. yes, 2.55, acidic
3. yes, 5.41, acidic
4. no, 1.12, acidic, 0.225 M Cl5. yes, 4.93, acidic
6. HCN and CN7. 0.32
*8. 50.0 mL 1.0 M NaX, 20.0 mL 1.0 M HCl, 30.0 mL H2O
*9. 2 mL
EXTRA 2B ANSWERS
1. (a) 3.10, acidic
(b) 3.11
(c) 3.14
2. (a) 3.09, acidic
(b) 2.99
(c) 3.19
1. (a) 20.0 mL
(b) 10.62
(c) 8.71
(d) 8.23
(e) 4.69
(f) 1.78
EXTRA 2C ANSWERS
(g)
(h) bromcresol green
2.
(f) 1 x 10-2, 1 x 10-6
) (g) bromphenol blue or methyl orange
( (h) o-cresolphthalein or phenolphthalein
*3. (a) 20.0 mL
(b) 3.65
(c) 6.12
(d) 6.60
(e) 7.08
(f) 9.71
(g) 12.15
(h) 2.5 x 10-7
(i) thymolphthalein
*4. 7 x 10-7
*5. HCO3- + H+ → H2O + CO2
H+ (from remaining HCl) + OH- → H2O
0.024 M
EXTRA 2D ANSWERS
1. 1.2 x 10-10
2. manganese (II) hydroxide
3. (a) 2 x 10-11 M, 2 x 10-9 g/L
(b) 5 x 10-21 M, 5 x 10-19 g/L
4. Yes
*5. (a) 3.5 x 10-7 M
(b) 6.3 x 10-11 M
*6. (a) 1.6 x 10-4 M
(b) 4.4 x 10-6 M
EXTRA 2E ANSWERS
1. 1.6 x 10-12 M
2. 17%
3. (a) Ag+
(b) 2.3 x 10-16 M
4. 1.5
5. 3.2 x 10-19 M and 3.2 x 101 M
*6. No precipitate will form
*7. 9 x 1012 M, 9 x 10-8 M
(c) 0.079 M
EXTRA 2F ANSWERS
1.
Isotope
Ne
17
Ne
18
Ne
19
Ne
20
Ne
21
Ne
22
Ne
23
Ne
24
Ne
25
Ne
26
Ne
27
Ne
28
Ne
29
Ne
30
Ne
31
Ne
32
Ne
33
Ne
34
Ne
Stable or Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Stable
Stable
Stable
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
Radioactive
16
2. (a)
19
9F

1
+
1H

(b)
176
(c)
11
6C

(d)
30
16S
+
(e)
26
71Lu
176
11
5B
8O
72Hf
-1e
+
+1β

(f)
8O
2
3. (a)
70
32Ge

70
(b)
80
35Br

80
36Kr
+
(c)
223
4
2α
+
219
(d)
26
87Fr
14Si
+
14
31Ga

0
-
-1e
4. (a) beta minus
ββββ-, β- n
β-, β- n
β-, β- n
β-, β- n, β- 2n
β-, β- n
ββn
β-, β- n
2α
-1β
-
+
2α
16

37.24 s
3.38 m
602 ms
197 ms
31.5 ms
18.9 ms
14.8 ms
7.3 ms
3.4 ms
3.5 ms
< 180 ns
> 60 ns
90.48%
0.27%
9.25%
15P
4
+
1H
Decay Mode
2p
β+ p
β+
β+
30
12Mg
+
0n
0
Half-Life
9 x 10-21 s
109.2 ms
1.6670 s
17.22 s
4
+
0
+

0
1
16
Natural Abundance

7N
2α
+
+1β
0
-1β
10Ne
4
0
+
26
23
+
+
-
85At
13Al
(b) beta plus or EC
(c) alpha or spontaneous fission
EXTRA 2G ANSWERS
1. 2.38 days
2. 5.3 years
3. 28.1 minutes
4. -968 years old
probably the result of French nuclear bomb testing in French Polynesia in the 1970’s, rendering
radiocarbon dating in the area inaccurate
5. 4.4 x 109 years
6. (a) 8.493 MeV/nucleon
*7. 77.32% 238U and 22.68% 235U
*8. 99.68% 238U and 0.32% 235U
(b) 7.977 MeV/nucleon