ADVANCED EXERCISES
CHAPTER 2 ATOMS AND THE ATOMIC
THEORY
1. Determine
a) The number of moles of Na in a
135 g. sample
b) The number of S atoms in 245 kg
sulfur
c) The mass of a one trillion (1x1012)
atom sample of copper
Ans: a)5,872 mol Na b) 4,601x 1027 S atoms
c)1,1 x 10-10 g Cu
2. Silicon has one major isotope,
28
𝑆𝑖 (27,97693 u), 92,21% natural
abundance) and two minor ones,
29
𝑆𝑖 (28,97649 u) and 30𝑆𝑖 (29,97376 u).
What are the percent natural abundances of
the two minor isotopes?
Ans: 29𝑆𝑖 = 4,71% ; 30𝑆𝑖 = 3,08%
3. A low melting Sn-Pb-Cd alloy called
eutectic alloy is analyzed. The mole ratio of
tin to lead is found to be 2,73:1 , and the mass
ratio of lead to cadmium is found to be 1,78:1
a) What is the percent composition of this
alloy, by mass?
b) What is the mass of a sample of this alloy
containing a total of 1 mol of atoms?
( Sn= 118,71 g/mol ; Pb=207,2 g/mol ;
Cd=112,41 g/mol)
Ans: a) Sn= 50,03% ; Pb=32% ; Cd=17,97%
b) 135,93 g
4. During a severe air pollution episode the
concentration of lead in air was observed to be
3,01 µg Pb / m3. How many Pb atoms would
be present in a 0,5 L sample of this
air(approximate lung capacity of a human
adult)?
(Pb=207,2 g/mol)
Ans: 4,37x1012 atoms
5.In each case, identify the element in question
if
a) an ion with a 2+ charge has 10% more
protons than electrons
b) an ion with a mass number of 110 and a 2+
charge has 25% more neutrons than electrons
c) its nucleus contains one more neutrons than
protons and the mass number is 9 times larger
than the charge on the ion X3+.
SHOW YOUR SOLUTION!!!
118
27
Ans: a) 48
𝑇𝑖
b)
𝑆𝑛
c)
13𝐴𝑙
22
50
CHAPTER 3. ELECTRONS IN ATOMS
1.Which of the following is the correct
ground-state electron configuration for
phophorus? Comment on the errors in each
of the others
a) [Ne] ( ) ( ) ( ) ( )
b) [Ne] (
)( )( )( )
c) [Ne] (
)(
)( )
d) [Ne] (
)( )( )( )
Ans: b
2.Use the basic rules for electron
configurations to indicate the number of
a) unpaired electrons in an atom of Si
b) 3d electrons in an atom of S
c) 4p electrons in an atom of As
d) 3s electrons in an atom of Sr
e) 4f electrons in an atom of Au
Ans : a) 2 b) 0 c) 3 d) 2 e) 14
3.What type of orbital(i.e 3s,4p,….) is
designated?
a) n=2 , l=1, ml=-1
b) n=4 , l=2 , ml=0
c) n=5 , l=0, ml=0
4.If traveling at equal speeds, which of the
following matter waves has the longest
wavelength? Explain and rearrange the
particles in the decreasing order of
wavelength
Electron, proton, neutron, alpha particle
Ans: λe >λp>λn>λα
5.Which of the following sets of quantum
numbers is/are not allowed? Why?
a) n=3 , l=2 , ml= -1
b) n=2 , l=3 , ml= -1
c) n=4 , l=0 , ml= -1
d) n=5 , l=2, ml= -1
e) n=3 , l=3, ml= -3
f) n=5 , l=3, ml= +2
6.Use condensed spdf notation to write out
the complete electron configuration of
a) Fluorine
b) Phophorus
c) Germanium
d) Tellurium. Do not use symbols such as
[Ne] or [Ar] for noble gas cores.
7.Indicate the number of unpaired electrons
in an atom
a) Calcium
b) Gallium
c) Iodine
d) Lead
CHAPTER 4- THE PERIODIC TABLE
1.Arrange the following elements according
to their first ionization energies
Rb, As, Sb, Br, Sr
Ans: Br>As>Sb>Sr>Rb
2.Arrange the following elements and ions
according to their sizes(atomic and/or ionic
radius:
N, Cs, As, Mg2+, Br 3.For the following groups of elements select
that has the property noted
a) the largest atom: H, Ar, Ag, Ba, Te, Au
b) the lowest first ionization energy: B, Sr,
Al, Br, Mg, Pb
c) the most negative electron affinity: Na, I,
Ba, Se, Cl, P
d) the largest number of unpaired electrons:
F, N, S-2, Mg+2, Sc+3 , Ti3+
4. Among the following ions, several pairs
are isoelectronic. Identify these pairs:
Fe+2, Sc+3, K+, Br-, Co+2, Co+3, Sr+2, O-2, Zn+2,
Al+3
5. Write the electron configuration of the
following ions
a) Rb+ :
b) Br - :
c) O-2 : 1 s2 2 s2 2 p6
d) Ba+2:
e) Zn+2: 1 s2 2 s2 2 p6 3 s2 3 p6 3 d10
f) Ag+:
g) Bi+3: 1 s2 2 s2 2 p6 3 s2 3 p6 4 s2 3 d10 4 p6 5
s2 4 d10 5 p6 6 s2 4 f14 5 d10
h) Cu2+ :
i) Ni+2:
j) Se-2:
k)Ti+2:
m) Cr+3:
5. Write the electron configurations of the
following ions and indicate whether they
are diamagnetic or paramagnetic. Indicate
also the number of unpaired electrons
a) K+
b) Cr+3
c) Zn+2:
d) Cd
e) Co+3
f) Sn+2
g) Br
Ans: a) diamagnetic- 0 unpaired electrons
b)paramagnetic-3 unpaired electrons
6.Arrange the following elements in order of
decreasing metallic character
Sc, Fe, Rb, Br, O, Ca, F, Te
Ans: Rb>Ca>Sc>Fe>Te>Br>O>F
7.Arrange the following elements in order of
decreasing densities:
Hg, As, Ti, Ni, Si, Pt, O
Hint: Densities of elements within a
PERIOD(from left to right) first increase
(until Group VIII B), then decrease but the
decrease in densities for each movement to
right is smaller than the increase
Densities of elements within a
GROUP(from top to bottom) increase as
atomic number increases
Elements with the greatest densities are at
the center of period 6.
Ans: Pt>Hg>Ni>As>Ti>Si>O
8.Which of the following elements has the
highest electrical conductivity:
Te, B, Ca, V, Ag, Fe, P
Hint: The metal which has one valence
electron is the most electrical conductive
CHAPTER 5-CHEMICAL COMPOUNDS
1- Determine the number of moles of Br2 in a
sample of consisting of
a) 3,52 x 1022 Br2 molecules
b) 4,86 x 1024 Br atoms
c) 188 g Bromine
d) 12,6 mL Bromine with a density of 3,1
g/mL
Ans: a) 0,0585 mol b) 4,035 mol c)1,175
mol
d)0,244 mol
2- Determine the mass percent of each of the
elements in the drug C20H24N2O2 (C=12
;H=1 ; N=14 ; O=16)
Ans: C: 74,1% ; H=? ; N=? ; O=?
3-What is the oxidation state of the
underlined element in each of the
following?
a) S8 b) Cr2O72- c)Cl2O d)KO2 e)CH4
f)SF4
g) FeO4-2
Ans: b) +6 c) +1
e) -4
4-Arrange the following anions in order of
increasing oxidation state(O.S)
a) SO32- b) S2O32- c) S2O82- d)HSO4 e)HS f)S4O62Ans: e<b<f<a<d<c
5- Hexachlorophene, used in making
germicidal soaps, has the following percent
composition by mass: 38,77% C ; 1,49%
H; 52,28% Cl ; 7,86% O. What is the
emprical formula of hexachlorophene?
Ans: C13H6Cl6O2
6- A compound of carbon and hydrogen
consists of 93,71% C and 6,29% H, by
mass. The molecular mass of the
compound is found to be 128 u. What is its
molecular formula?
7- Name the compounds
a) ZnO b) Cs2SO4 c) FeSO4 d)
(NH4)2HPO4 e)Cu(OH)2
f) KClO4 g)LiCN h)H3PO3
Ans: c) Iron(II)sulfate
e)
Copper(II)hydroxide
f)Potassiumperchlorate
g)Lithiumcyanide
8-Write correct formulas for the compounds
a)Ammoniumdichromate
b)Lead(II)acetate
c)Tricarbondisulfide
d)Strontiumnitrite
e)Calciumdihydrogenphosphate
f) Iodic acid
g) Phosphorus dichloride trifluoride
Ans: a) (NH4)2Cr2O7 b) Pb(C2H3O2)2
e)Ca(H2PO4)2
9-Paracresol is used as a disinfectant and in
the manufacture of herbicides and
artificial food flours. A 0,401 g sample of
this carbon-hydrogen-oxygen compound
yields 1,144 g CO2 and 0,2671 g H2O in
combustion analyses. What is the
empirical formula of paracresol? (C=12 ;
H=1 ; O=16)
Ans: C7H8O
10- What mass of BHA(C11H16O2) should be
burned to produce 0,5 g CO2 in
combustion analysis? (C=12 ; H=1 ;
O=16)
Ans: 0,186 g
11- A sample of MgSO4 ∙ X H2O weighing
8,129 g is heated until all the water of
hydration is driven off. The resulting
anhydrous compound, MgSO4 weighs
3,967 g. What is the formula of this
hydrate? X=?
CHAPTER 6-GASES
1- A 14,7 L cylinder contains 46,7 g O2 at
35˚C. What is the pressure of this gas, in
atm?
Ans: 2,5 atm
2- A 10 g sample of a gas has a volume of
4,62 L at 35˚C and 762 mmHg. If to this
content 4,62 L volume is added 2,3 g of the
same gas and the temperature raised to
51˚C, what is the new gas pressure?
Ans: 986 mmHg
3- A sample of N2 (g) occupies a volume of
58 mL under the existing barometric
pressure. Increasing the pressure by 125
mmHg reduces the volume to 49,6 mL.
What is the prevailing barometric pressure
in mmHg?
Ans: 738 mmHg
4-A particular gaseous hydrocarbon that is
82,7%C and 17,3% H by mass has a
density of 2,35 g/L at 25˚C and 752 mmHg.
What is the molecular formula of this
hydrocarbon?
Ans: C4H10
5- 1,5 L H2S (g) measured at 23˚C and 735
mmHg, is mixed with the 4,45 L O2(g) ,
measured at 26,1˚C and 751 mmHg and
burned
2 H2S(g) + 3 O2(g)
2 SO2(g) + 2
H2O(g)
a) How much SO2(g) in moles is produced?
b) If the excess reactant and products are
collected at 748 mmHg and 120˚C, what
volume in L will they occupy?
Ans: a) 0,0597 mol
b) 6,88 L
6- A mixture of 4 g H2(g) and an unknown
quantity of He(g) is maintained at STP. If
10 g H2(g) is added to the mixture while
conditions are maintained at STP, the gas
volume doubles. What mass of He is
present?
Ans: 12 g.
7- Producer gas is a type of fuel gas made by
passing air or steam through a bed of hot
coal or coke. A typical producer gas has the
following composition in percent by
volume: 8,0% CO2, 23,2% CO, 17,7% H2,
1,1% CH4 and 50% N2
a) What is the density of this gas at 25˚C and
752 mmHg, in g/L?
b) What is the partial pressure of CO in this
mixture at STP?
Ans: a) 0,993 g/L b) 0,232 atm
8- What is the partial pressure of Cl2(g), in
mmHg, in a gaseous mixture at STP that
consists of 50% N2, 22,3% Ne and 27,7%
Cl2 by mass?
Ans: 90 mmHg
9- The root mean square speed, urms of H2
molecules at 273 K is 1,84x103 m/s. At
what temperature is urms for H2 twice this
value?
Ans: 1094,5 K
10- If 0,00312 mol N2O(g) effuses through
an orifice in a certain period of time, how
much NO2(g) would effuse in the same
time under the same conditions?(N=14 ;
O=16)
Ans: 3,051x 10-3 mol
11- Without doing detailed calculations,
determine which of the following gases has
the greatest density at STP?
Cl2, SO3, N2O, PF3
12-Under which of these conditions is Cl2
most likely to behave like an ideal gas?
Explain!!!
a) 100˚C and 10 atm
b) 0˚C and 0,5 atm
c) 200˚C and 0,5 atm
d) - 100˚C and 10 atm
CHAPTER 7-THERMOCHEMISTRY
1-What are the internal energy changes, ΔU,
if a system
a) absorbs 67 J of heat and does 67 J of
work?
b) Absorbs 356 J of heat and does 592 J of
work?
c) Loses 38 J of heat and has 171 J of work
done on it?
d) Absorbs no heat and does 416 J of work?
2-A bomb calorimetry experiment is
performed with isobutane, (CH3)3CH, as
the combustible substance. The data
obtained are
Mass of isobutane burned: 1,036 g
Heat capacity of calorimeter: 4,947 kJ/˚C
Initial calorimeter temperature: 24,88˚C
Final calorimeter temperature: 35,17˚C
a) What is the heat of combustion of
isobutane in kJ/mol?
b) Write the chemical equation for the
complete combustion of isobutane and
represent the value of ΔH in this equation?
Hint: Assume for this reaction qv=qP and
ΔU=ΔH
Ans: a) – 2856 kJ/mol
3-The combustion of hydrogen-oxygen
mixtures is used to produce very high
temperatures(ca. 2500˚C) needed for
certain types of welding operations.
Consider the reaction to be:
H2(g) + ½ O2(g)
H2O(g) ΔH= - 241,8
kJ
What is the quantity of heat in kJ evolved,
when a 105 g mixture containing equal
parts of H2 and O2 by mass, is burned?
Ans: - 793 kJ
4- The combustion of 1 g of thiourea,
CS(NH2)2 (s) in a bomb calorimeter(at
constant volume) evolves 15,37 kJ of heat
at 25˚C. The products of the combustion
are CO2(g), SO2(g), N2(g) and H2O(l)
a) What is ΔU for the combustion of 1
mol thiourea?(C=12 ; S=32; O=16 ;
N=14 ; H=1)
b) Write the chemical equation for the
reaction.
c) What is the ΔH for the combustion?
Ans: a) 1170 kJ/mol
5-For the reaction at 25˚C :
CaNCN(s) + 3 H2O(l)
CaCO3(s) + 2
NH3(g)
ΔU= - 261,75 kJ
ΔHCaCO3= - 1206,9 kJ
ΔHNH3= - 46,19 kJ
ΔHH2O= -285,9 kJ
Calculate the enthalpy of formation of
CaNCN(s)
Ans: - 184,78 kJ
6-Use Hess’s Law and the following data
I- CH4(g) + 2 O2(g)
CO2(g) + 2
H2O(g) ΔH= - 802 kJ
II- CH4(g) + CO2(g)
2 CO(g) + 2
H2(g) ΔH= + 206 kJ
III- CH4(g) + H2O(g)
CO(g) + 3
H2(g) ΔH= + 247 kJ
To determine ΔH for the reaction:
CH4(g) + ½ O2(g)
CO(g) + 2 H2(g)
7- Determine ΔH for the reaction :
N2H4(l) + 2 H2O2(l)
N2(g) + 4
H2O(l)
From these data:
I- N2H4(l) + O2(g)
N2(g) + 2
H2O(l) ΔH= - 622,3 kJ
II- H2(g) + ½ O2(g)
H2O(l) ΔH= 285,8 kJ
III- H2(g) + O2(g)
H2O2 (l) ΔH= 187,8 kJ
8- Calculate ΔH for the synthesis of 1 mol C5H12(l) from CO(g) and H2(g):
5 CO(g) + 11 H2(g)
C5H12(l) + 5 H2O(l) ΔH=?
If ΔH= - 3534 kJ fort he complete combustion of one mole of pentane, C5H12(l) ;
ΔHCO2= - 393,5 kJ/mol, ΔHH2O= - 285,8 kJ/mol , ΔHCO= -110,5 kJ/mol
Hint: You can get ΔH C5H12(l) through the
combustion reaction(Write first the
combustion reaction and calculate ΔH
C5H12(l))
Ans: - 1024,8 kJ
9-Some of the butane(C4H10 (g)) in a 200 L
cylinder at 26˚C is withdrawn and burned
at constant pressure in excess of air. As a
result the pressure of the gas in the cylinder
falls from 2,35 atm to 1,1 atm. The
liberated heat is used to raise the
temperature of 132,5 L of water from 26˚
to 62,2˚C. Assume that the combustion
products are CO2(g) and H2O(l) and
determine the efficiency of the water
heater. (that is, what percent of heat of
combustion was absorbed by the water? )
CpH2O =4,18 J/g˚C
dH2O= 1 g/mL
ΔHC4H10= - 125,7 kJ/mol
ΔHCO2 = - 393,5 kJ/mol
ΔHH2O= - 285,8 kJ/mol
Ans: 68,38%
CHAPTER 8-SOLUTIONS AND THEIR
PHYSICAL PROPERTIES
1-A solution (d= 1,235 g/mL) is 90%
glycerol(C3H8O3) and 10% H2O, by mass.
Determine
a) The molarity of C3H8O3 (with H2O as the
solvent)
b) The molarity of H2O( with C3H8O3 as the
solvent)
c) The molality of H2O in C3H8O3
d) The mole fraction of C3H8O3
e) The mole percent of H2O
Ans: a) 12,078 M c) 6,173 m e) 36,2%
2. Styrene, used in manufacture of polystrene
plastics is made from ethylbenzene by the
extraction of hydrogen atoms. The product
obtained contains about 38% styrene(C3H8)
and 62% ethylbenzene(C8H10) by mass.
The mixture is seperated by fractional
distillation at 90˚C. Determine the
composition of the vapor in equilibrium
with this 38-62% mixture at 90˚C given the
vapor pressures of two components:
ethylbenzene=182 mmHg ; styrene=134
mmHg
Ans: XC3H8= 0,521 ; XC8H10=0,479
3.A compound is 42,9% C; 2,4% H ; 16,7%N
and 38,1% O by mass. Addition of 6 g of
this compound to 50 mL benzene,
C6H6(d=0,879 g/mL) lowers the freezing
point from 5,53˚ to 1,37˚C. What is the
molecular formula of this compound? (KF
for benzene= 5,12˚C/m-1)
Ans: C6H4N2O4
4.The solubility of O2 in water is 2,18x10-3
M at 0˚C and 1,26x10-3 M at 25˚C. What
volume of O2(g) measured at 25˚C and 748
mmHg, is expelled when 285 mL water is
heated from 0˚C to 25˚C?
Ans: 9,2 mL
5.Calculate the osmotic pressure of a
solution in bars which contains 3 g NaOH
and has a volume of 60 cm3 at 30˚C. The
percent ionization, α=85% and i=1 + α(n-1)
(Na=23 ; O=16 ; H=1)
Ans: 58,21 bar
6. (Genel Kimya, s.283) A volatile and
nonelectrolyte substance having a mass of
6,84 g is dissolved in 100 g of water. The
vapor pressure of the solution at 25˚C is
measured 3,11x10-2 bar and the vapor
pressure of water at25˚C is 3,17x10-2 bar.
Calculate the molecular weight of the
substance.
Ans: 62,18 g/mol
CHAPTER 9-CHEMICAL KINETICS
1.Given the reaction A(g) +2 B(g)
products. The data obtained according to
this reaction is as follows:
Experime
Initial
Rate of
nt
Concentratio reaction(mol/L
n (mol/L)
s)
[A]0
[B]0
1
0,6
0,3
12,6
2
0,2
0,3
1,4
3
0,6
0,1
4,2
4
0,17
0,25 ?
a) What is the order of reaction in A and B?
b) Write the rate equation
c) Calculate the rate constant
d) Calculate the rate of reaction in
Experiment 4
Ans: c) 116,67 L2mol-2s-1 d) 0,843 molL-1s1
2.Given the reaction A(g) + B(g) +C(g)
products. The data obtained according to
this reaction is as follows:
Experime
Initial
Rate of
nt
Concentratio reaction(mol/L
n (mol/L)
s)
[A] [B] [C]
0
1
2
3
4
5
0
0
1,2 1,2 1,2
5
5
5
2,5 1,2 1,2
5
5
1,2 3,0 1,2
5
2
5
1,2 3,0 3,7
5
2
5
3,0 1,0 1,1
1
5
8,7
17,4
50,8
457
?
a) What is the order of reaction in A and B
and C?
b) Write the rate equation
c) Calculate the rate constant
d) Calculate the rate of reaction in
Experiment 5
3. In a first order reaction, dinitrogenpentoxide is decomposed to NO2 (g)and O2(g) at
328K. The table below shows the change in the total pressure of the reaction vessel
with time
Time, min
Total pressure,
kPa
0
5
10
15
20
30
27,3
43,7
53,6
59,4
63
66,3
a)
b)
c)
d)
e)
f)
g)
Write the decomposition reaction
What are the partial pressures of NO2 (g)and O2(g) at t=10 min
Caluculate the rate constant in terms of L/molmin
Determine the half life of the reaction
Calculate the rate of reaction at t=20 min
How many minutes does it take to decompose 80% of dinitrogenpentoxide?
Assume now some of O2 (g) produced by the decomposition reaction is removed from
the vessel at t=15 min and dissolved in water at 328˚K. The solubility of O2 (g) in
saturated water at 328˚K is measured 5,45x10-5 mol/L . If the aqueous solubility of O2
at STP is 48,9 mL per Liter, calculate the mole percentage of O2 remained in the
reaction vessel(% O2=?)
h) Assuming that the reaction vessel has a volume of 10 L, what is the time in minutes
required to produce 1,12 g of O2
i) Calculate the mole fraction and mass percentage (%) of NO2 at t=8 min in the
gaseous mixture
(1 atm=101,325 kPa ; N=14 ; O=16)
4.The half life of the reactant A is 50,5 s in a
second order reaction where its initial
concentration is [A]0= 0,84 molL-1.
a) Calculate the rate constant
b) Calculate the reaction rate at t=30 s
c) What is the time required so that 15/16 of
the reactant A will be consumed?
5. The first order reaction A
products
has a half-life of 46,2 min at 25˚C and 2,6 min
at 102˚C
a) Calculate the activation energy, Ea of this
reaction
b)At what temperature would the half-life be
10 min?
CHAPTER 10- CHEMICAL EQUILIBRIUM
1-A sample of air is with an original mole ratio
of N2 to O2 of 79:21 is heated to 2500K. When
equilibrium is established, the mole percent of
NO is found to be 1.8%. Calculate KP for the
reaction
N2(g) + O2 (g)
2500 K
2 NO(g) Kp=? At
2-A phosphoruspentachloride sample having a
mole content of 0,1 mol was introduced into a
3 L container which contains Cl2(g) at 0,5 atm
at 250˚C. If the equilibrium is established later
at the given temperature and the Kp value is
given below, calculate the dissociation rate of
PCl5(g) in %
PCl5(g)
PCl3(g) + Cl2(g) Kp= 1,78
3-For the synthesis of ammonia at 500 K,
N2(g) +3 H2(g)
2 NH3(g), Kp=9,06x10-2.
Assume that N2 and H2 are mixed in the mole
ratio 1:3 and the total pressure is maintained at
1 atm. What is the mole% NH3 at equilibrium?
4-Nitrogen dioxide obtained as a cylinder gas
is always a mixture of NO2(g) and
N2O4(g). A 5 g. sample obtained from such
a cylinder is sealed in a 0,5 L flask at
298K. What is the mole fraction of NO2 in
this mixture?
N2O4(g)
2 NO2(g) Kc=4,61x10-3
Ans: 0,177
5-In the manufacture of ammonia, the chief
source of hydrogen gas is this reaction for
the reforming of methane at high
temperatures.
CH4(g) + 2 H2O (g)
CO2(g) + 4 H2(g)
The following data are also given:
1) CO(g) + H2O(g)
CO2(g) +
H2(g) ΔH= - 40 kJ ; Kc=1,4 at 1000K
2) CO(g) + 3 H2(g)
H2O(g) +
CH4(g) ΔH= - 230 kJ ; Kc=190 at 1000K
A gaseous mixture is prepared containing
0,1 mol each of CH4(g), H2O(g), CO2(g),
H2(g) in a 5 L flask. Then the mixture is
allowed to come to equilibrium at 1000K
in reaction.
a) What will be the equilibrium amount,
in moles of each gas?
b) Describe the effect on the equilibrium
amount of H2 produced by each of these
actions
1- Add a catalyst
2- Add CH4
3- Add CO2
4- Add He(g) at constant volume
567-
Remove H2O
Raise the temperature to 1200K
Transfer the mixture to a 15 L flask