Download Complete the following equations

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Gas chromatography–mass spectrometry wikipedia , lookup

Electron configuration wikipedia , lookup

Acid wikipedia , lookup

Marcus theory wikipedia , lookup

Ion wikipedia , lookup

Electronegativity wikipedia , lookup

Catalysis wikipedia , lookup

Nitrogen wikipedia , lookup

Periodic table wikipedia , lookup

Fluorochemical industry wikipedia , lookup

History of chemistry wikipedia , lookup

Hydroxide wikipedia , lookup

Inorganic chemistry wikipedia , lookup

Redox wikipedia , lookup

X-ray fluorescence wikipedia , lookup

Transition state theory wikipedia , lookup

Freshwater environmental quality parameters wikipedia , lookup

Abundance of the chemical elements wikipedia , lookup

Metalloid wikipedia , lookup

Nucleophilic acyl substitution wikipedia , lookup

Photosynthesis wikipedia , lookup

Biochemistry wikipedia , lookup

Artificial photosynthesis wikipedia , lookup

Ionization wikipedia , lookup

PH wikipedia , lookup

Electrochemistry wikipedia , lookup

Acid rain wikipedia , lookup

Chemistry: A Volatile History wikipedia , lookup

Bioorthogonal chemistry wikipedia , lookup

Stoichiometry wikipedia , lookup

Acid–base reaction wikipedia , lookup

Lewis acid catalysis wikipedia , lookup

Hypervalent molecule wikipedia , lookup

Strychnine total synthesis wikipedia , lookup

Halogen wikipedia , lookup

Microbial metabolism wikipedia , lookup

Gaseous signaling molecules wikipedia , lookup

Ununennium wikipedia , lookup

Water splitting wikipedia , lookup

Metalloprotein wikipedia , lookup

Evolution of metal ions in biological systems wikipedia , lookup

Unbinilium wikipedia , lookup

Photosynthetic reaction centre wikipedia , lookup

Calcium looping wikipedia , lookup

Atomic theory wikipedia , lookup

Alkaline earth metal wikipedia , lookup

Electrolysis of water wikipedia , lookup

Transcript
Chem 1B
Chapter 20 Exercises with Answers
Exercise #1:
1.
(a) Explain the general trends of atomic size across a period and down a group in the periodic table for
main group elements.
(Answer: Atomic size decreases left-to-right across periods and increases top-to-bottom down a group. This
is due to increasing effective nuclear attraction on valence-shell electrons across periods and the increasing
size of valence-shell as the principal quantum number n increases down a group.)
(b) What factor(s) influence the atomic size of an element?
(Answer: As size decreases from left to right across periods, the first ionization energy, electron affinity, and
electronegativity increase from left to right; while the metallic characteristics of the elements decreases and
nonmetallic properties increase. As atomic size gets larger when going down a group, ionization energy
decreases, metallic characteristics increase and reactivity of metals increases.)
(c) How does atomic size influence the following properties of atoms?
(i) Ionization energy:
(Atomic size decreases, ionization energy decreases, and vice versa.)
(ii) Electron affinity;
(Atomic size decreases, electron affinity increases)
(iii) Electronegativity;
(Atomic size decreases, electronegativity increases)
(iv) Reactivity of elements.
(Atomic size increases from left to right and down the group, ionization energy decreases and
reactivity of metals increases. Atomic size decreases across periods and going up a group,
electronegativity increases and reactivity of nonmetal elements increases.)
2.
While ionization energy generally increases from left to right across period in the periodic table, a
certain anomaly is observed in this trend. For example, in the second period, ionization energy
decreases from Be to B and from N to O; in the third period, ionization energy decreases from Mg to Al
and from P to S. Explain why the anomaly.
(In beryllium electron is removed from 2s orbital, but it is removed from 2p orbital in boron. It is easier to
remove an electron from a 2p orbital since it has a slightly higher energy level than 2s. For the same
reasoning, it is easier to remove an electron from a 3p orbital (in Al) than to remove one from a 3s orbital
(Mg). Nitrogen has a half-filled 2p orbital that give it a more stable electron configuration and more difficult
to remove the electron; while in oxygen one of the 2p orbital is doubly occupied and the existence of electronelectron repulsion causes a small de-stabilizing effect and easier to remove the electron.)
3.
How do the metallic characteristics of elements vary across periods and down the groups, respectively,
in the periodic table?
(Metallic properties decrease left-to-right across periods and increases down the group.)
4.
How do the ionic and acid-base properties of oxides of elements in the third period of the periodic table
vary from left to right?
(Ionic property decreases from left to right; the oxides of metals are basic and those of nonmetals
are acidic. The oxides become less basic and more acidic from left to right of the periodic table.)
5.
How do the ionic and acid-base properties of the oxides of Group 3 elements vary from top to bottom?
(Ionic properties of Group 3 elements increase from top to bottom going down the group. The
oxides change from being weakly acidic to amphoteric to basic. B2O3 is weakly acidic, Al2O3 and
Ga2O3 are amphoteric, In2O3 and Tl2O3 are basic, and Tl2O is strongly basic.)
1
Chem 1B
Chapter 20 Exercises with Answers
6.
Name five most abundant elements (by mass) in the Earth’s crust and five most abundant elements in
the human body.
(In Earth’s crust: Oxygen, Silicon, Aluminum, Calcium, Iron;
In human body: Oxygen, Carbon, Hydrogen, Nitrogen, Calcium.)
7.
What are three most abundant elements in the atmosphere?
(Nitrogen, Oxygen, and Argon)
8.
How is hydrogen different from the other elements in Group 1A? What are the three isotopes of
hydrogen? Which isotope of hydrogen is radioactive?
(Hydrogen is a nonmetal and has much higher ionization energy than any of the alkali metal.
Isotopes: protium (1H), deuterium (2H), and tritium (3H); tritium is radioactive.)
9.
Write balanced equations for the laboratory preparation of hydrogen gas and for the industrial
preparation of hydrogen gas.
Lab preparation of H2: Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g);
Industrial process: CH4(g) + H2O(g)  CO(g) + 3H2(g);
Ho = +206)
10.
Give three industrial uses of hydrogen gas and write a balanced equation for each of them.
(a) Production of ammonia: N2(g) + 3H2(g)  2NH3(g);
(b) Production of methanol: CO(g) + 2H2(g)  CH3OH(l);
(c) production of hydrochloric acid: H2(g) + Cl2(g)  2HCl(g)  2HCl(aq)
2
Chem 1B
Chapter 20 Exercises with Answers
Exercise #2:
A. Complete and balance each of the following equations:
2HCl(aq)  MgCl2(aq) + H2(g)
1.
Mg(s) +
2.
MgH2(s) + 2H2O(l)  Mg(OH)2(s) + 2H2(g)
3.
CH4(g) + H2O(g)  CO(g) + 3H2(g)
4.
C(s) + H2O(hot steam)  CO(g) + H2(g)
5.
2Na(s) +
6.
Ca(s) +
7.
2Li(s) + H2(g)  2LiH(s)
8.
N2(g) + H2(g)  2NH3(g)
9.
4Li(s) + O2(g)  2Li2O(s)
10.
2Na(s) + O2(g)  Na2O2(s)
11.
K(s) +
12.
2Mg(s) + O2(g)  2MgO(s)
13.
2Ca(s) + O2(g)  2CaO(s)
14.
Ba(s) + O2(g)  BaO2(s)
15.
6 Li(s) + N2(g)  2Li3N(s)
16.
3Mg(s) + N2(g)  Mg3N2(s)
17.
Li3N(s) +
18.
Na2O2(s) +
2H2O(l)  2NaOH(aq) + H2O2(aq)
19.
4KO2(s) +
2CO2(g)  2K2CO3(s) + 3 O2(g)
20.
Li2CO3(s) + heat  Li2O(s) + CO2(g)
21.
2NaHCO3(s) + heat  Na2CO3(s) + H2O(g) + CO2(g)
22.
CaCO3(s) + heat  CaO(s) + CO2(g)
2H2O(l)  2NaOH(aq) + H2(g)
2H2O(l)  Ca(OH)2(aq) + H2(g)
O2(g)  KO2(s)
3H2O(l)  3LiOH(aq) + NH3(g)
3
Chem 1B
Chapter 20 Exercises with Answers
23.
CaO(s) + SO2(g)  CaSO3(s)
24.
2Al(s) + 3 O2(g)  Al2O3(s)
25.
2Al(s) +
3 Cl2(g)  AlCl3(s)
26.
2Al(s) +
6HCl(aq)  2AlCl3(aq) + H2(g)
27.
Al2O3(s) +
28.
Al2O3(s) + 2NaOH(aq) + 3H2O(l)  2NaAl(OH)4(aq)
29.
Na2CO3(aq) + 2HCl(aq)  2NaCl(aq) + H2O(l) + CO2(g)
30.
CO(g) + H2(g) 
31.
2 C8H18(l) + 25 O2(g)  16 CO2(g) + 18 H2O(l)
32.
SiO2(s) + 4 HF(g)  SiF4(g) + 2 H2O(g)
33.
SiCl4(g) + 2 Mg(s)  Si(s) + 2 MgCl2(s)
34.
Sn(s) + O2(g)  SnO2(s)
35.
Pb(s) + O2(g)  PbO(s)
3H2SO4(aq)  Al2(SO4)3(aq) + 3H2O(l)
CH3OH(l)
B. Give one use for each of the following compounds:
(a) Lithium bromide (LiBr): (as dehumidifier in air-conditioning system)
(b) Lithium carbonate (Li2CO3): (manufacture of a special glass and treatment of manic depression)
(c) Sodium carbonate (Na2CO3): (glass manufacture)
(d) Sodium bicarbonate (NaHCO3): (baking; fire-extinguisher)
(e) Sodium hydroxide (NaOH): (a strong base; manufacture of bleach solution)
(f) Sodium chloride (NaCl): (food and dietary requirement; source of sodium)
(g) Magnesium carbonate (MgCO3): (Source of magnesium)
(h) Calcium oxide (quicklime, CaO): (steel manufacture; manufacture of cement; pollution control)
(i) Calcium chloride (CaCl2): (production of calcium by electrolysis)
(j) Aluminum sulfate (Al2(SO4)3); (treatment of municipal water)
4
Chem 1B
Chapter 20 Exercises with Answers
Exercise #3:
1.
Rank the alkaline metals in order of ionization energy and reactivity.
Ionization energy: Cs < Rb < K < Na < Li;
2.
Reactivity: Li < Na < K < Rb < Cs.
Name some common and important compounds of sodium; write their formulas, and their uses.
NaCl: source for Na and Cl2, included in food for electrolyte balance and as food preservative;
NaOH: a strong base and drain cleaner;
NaOCl: bleach solution;
NaHCO3: baking soda and fire-extinguisher;
Na2CO3: glass manufacture.
3.
4.
Write the major product in each of the following reactions between lithium, sodium and potassium
metals with oxygen gas.
(a) Li(s) + O2(g)  ?
(Li2O(s))
(b) Na(s) + O2(g)  ?
(Na2O2(s))
(c) K(s) + O2(g)  ?
(KO2(s))
Briefly explain the production of sodium metal from NaCl.
Electrolysis of molten NaCl produces Na at cathode and Cl2 at anode.
5.
Rank the alkaline Earth metals in order of increasing reactivity.
Be < Mg < Ca < Sr < Ba < Ra
6.
In what ways is beryllium different from other Group 2A elements? What factor (or factors) makes
beryllium different from the other metallic elements?
Beryllium has a very high ionization energy and the formation of ion is not favorable. All compounds of
beryllium are covalent molecules. BeO is amphoteric; while MgO, CaO, SrO, etc. are basic. BeCl2 is a
covalent molecule; while MgCl2, CaCl2, SrCl2, and BaCl2 are ionic compounds.
7.
Briefly describe the Dow’s process for the production of magnesium from seawater. Provide a balanced
equation for each step involved.
(1) Magnesium is precipitated from seawater as Mg(OH)2 by treating the seawater with CaO:
(Mg2+(aq) + CaO(s) + H2O(l)  Mg(OH)2(s) + Ca2+(aq))
(2) Mg(OH)2 is filtered and treated with HCl: (Mg(OH)2(s) + 2HCl(aq)  MgCl2(aq) + H2O)
(3) MgCl2 is evaporated to dryness and the solid is melted. Molten MgCl2 is electrolyzed to obtain
Mg and Cl2.
8.
The concentration of Mg2+ in seawater is about 0.055 M. (a) How many liters of seawater will produce
1.00 kg of magnesium. (b) How many kilograms of calcium oxide, CaO, must be added to the seawater
sample of part (a) in order to precipitate all of Mg2+ as magnesium hydroxide. (c) Write a balanced
equation for reaction that involves Mg2+(aq), CaO(s), and H2O to produce Mg(OH)2(s).
(Answer: (a) 748 L; (b) 2.31 kg; (c) Mg2+(aq) + CaO(s) + H2O(l)  Mg(OH)2(s) + Ca2+(aq))
5
Chem 1B
Chapter 20 Exercises with Answers
9.
Write a balanced equation for each of the following reactions:
(a) Calcium reacts with oxygen to form calcium oxide:
(2Ca(s) + O2(g)  2CaO(s))
(b) Barium reacts with oxygen to form barium peroxide: (Ba(s) + O2(g)  BaO2(s))
(c) Magnesium reacts with silicon tetrachloride vapor to produce silicon and magnesium chloride.
(2Mg(s) + SiCl4(g)  Si(s) + 2MgCl2(s))
(d) Magnesium nitride reacts with water to produce magnesium hydroxide and ammonia.
(Mg3N2(s) + 6H2O(l)  3Mg(OH)2(s) + 2NH3(aq))
(e) Calcium carbonate reacts with hydrochloric acid solution to produce aqueous calcium chloride,
water and carbon dioxide gas.
(CaCO3(s) + 2HCl(aq)  CaCl2(aq) + H2O(l) + CO2(g))
10.
Give THREE major uses of magnesium metal.
(1) Manufacture of light alloys for air-craft body;
(2) Reducing agent in isolation of B, Si, and Ti;
(3) fire-work, flare and flash photography.
11.
Give THREE important compounds of calcium and their uses.
(1) CaO: manufacture of cement;
(2) CaCO3: manufacture of CaO and steel production.
(3) Ca(OH)2: manufacture of bleach powder)
12.
Write a balanced equation for each reaction described below:
(a) Reaction of calcium metal with water to form hydrogen gas and aqueous calcium hydroxide.
Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g);
(b) Reaction of solid calcium carbonate with dilute hydrochloric acid and the products are aqueous
calcium chloride, water, and carbon dioxide gas.
CaCO3(s) + 2HCl(aq)  CaCl2(aq) + H2O(l) + CO2(g)
(c) Reaction of calcium hydroxide solution (or limewater) with carbon dioxide gas to form calcium
carbonate and water.
The Production of Magnesium from Seawater.
1.
Mg2+(aq) + Ca(OH)2(aq)  Mg(OH)2(s) + Ca2+(aq)
2.
Mg(OH)2(s)  MgO(s) + H2O(g)
3.
MgO(s) + 2HCl(aq)  MgCl2(aq) + H2O(l)
4.
MgCl2(aq) (goes into a dryer)  MgCl2(s) (melted)  MgCl2(l) (electrolysis)  Mg(l) + Cl2(g)
6
Chem 1B
Chapter 20 Exercises with Answers
The Production of Magnesium from MgCO3 (Dolomite):
1.
MgCO3(s)  MgO(s) + CO2(g)
2.
MgO(s) + 2HCl(aq)  MgCl2(aq) + H2O(l)
3.
MgCl2(aq) (goes into a dryer)  MgCl2(s) (melted)  MgCl2(l) (electrolysis)  Mg(l) + Cl2(g)
Production of Calcium from CaCO3:
1.
CaCO3(s)  CaO(s) + CO2(g)
2.
CaO(s) + 2HCl(aq)  CaCl2(aq) + H2O(l)
3.
CaCl2(aq) (goes into a dryer)  CaCl2(s) (melted)  CaCl2(l) (electrolysis)  Ca(l) + Cl2(g)
Exercise #4:
1.
Write the chemical formula and the name of each of the following compounds of Group 3A:
(a) An acidic oxide:_B2O3_________
(b) An amphoteric oxide: __Al2O3___________
(c) Most basic oxide of Group 3 elements: __Tl2O__________;
(d) A compound composed of lithium boron and hydrogen that is used as a reducing agent in organic
synthesis: _LiBH4__________
(e) An aluminum compound used for the treatment of municipal water: __Al2(SO4)3__________
2.
In the production of aluminum by electrolysis, electrolytic cells operating at 5.0 V and 1.5 x 105 A is
used. (a) How many kilograms of Al can be produced in 1.00 hour of electrolysis? (b) How much
energy (in kWh) is consumed during this operation? (Answer: (a) 50.3 kg; (b) 750 kWhr)
3.
Write a balanced equation for each reaction described below:
(a) Aluminum metal reacts with dilute hydrochloric acid to yield aqueous aluminum chloride and
hydrogen gas.
(2Al(s) + 6HCl(aq)  2AlCl3(aq) + 3H2(g))
(b) Aluminum reacts with nitric acid to produce aluminum oxide(s), nitric oxide, and water.
(2Al(s) + 2HNO3(aq)  Al2O3(s) + 2NO(g) + H2O(l))
(c) Aluminum oxide reacts with sulfuric acid to form aluminum sulfate and water.
(Al2O3(s) + 3H2SO4(aq)  Al2(SO4)3(s) + 3H2O(l))
4.
Give THREE major uses of aluminum metal.
(1) manufacture of light alloys for aircraft body and engine;
(2) beverage cans;
(3) reducing agent in rocket fuel.
7
Chem 1B
Chapter 20 Exercises with Answers
5.
Briefly describe the extraction of silicon from silicon dioxide (sand):
SiO2(s) + 2C(s)  Si(s) + 2CO(g);
Si(s) + 2Cl2(g)  SiCl4(g);
SiCl4(g) + 2Mg(s)  Si(s) + 2MgCl2(s);
6.
How does silicon dioxide differ from carbon dioxide in term of their molecular structures and chemical
and physical properties?
(SiO2 does not form a discrete molecule like CO2; instead, SiO2 forms a covalent network solid.)
7.
What is the major difference between carbon-based polymers and silicon-based polymers?
(Carbon polymers are carbon-carbon chains, but silicon polymers are -Si-O-Si- chains)
8.
Given the following oxides of Group 4A elements: CO2, SiO2, GeO2, SnO, SnO2, PbO, and PbO2,
indicate which oxides are acidic, which are amphoteric, and which are basic?
(CO2, SiO2, GeO2, SnO2 and PbO2 are acidic oxides; SnO and PbO are amphoteric)
Exercise #5:
1.
Explain the trend of metallic and non-metallic characters of the Group VA elements. Which element
has the highest ionization energy and which has the lowest ionization energy?
(Metallic characters increase down the group; nitrogen has the highest ionization energy and bismuth has the
lowest ionization energy.)
2.
Describe (briefly) the industrial method used to extract nitrogen gas from the atmosphere. Give two
major industrial uses of nitrogen gas.
(Uses of nitrogen gas: (1) manufacture of NH3; (2) refrigeration; (3) provide an inert blanket for oxygensensitive materials)
3.
4.
What is the oxidation number/state of nitrogen in each of the following species?
(a) N2 (0)
(b) NH3 (3)
(c) N2H4 (-2)
(d) NH2OH (-1)
(e) NF3 (+3)
(f) NO (+2)
(g) NO2 (+4)
(h) N2O (+1)
(i) HNO3 (+5)
(j) NaNO2 (+3)
The reaction between nitrogen and chlorine gas produces nitrogen trichloride, NCl3, as the sole product.
However, reactions between phosphorus, Arsenic, and antimony with chlorine gas will produce both
trichloride, MCl3, and pentachloride compounds (MCl5). Explain why nitrogen (a member of Group 5A
elements) will not form pentachloride.
(Nitrogen cannot form NCl5 because nitrogen atom is a second period element, which an outermost shell (n =
2) cannot accommodate more than 8 electrons. P, As, and Sb have the outermost-shell with n > 2; each can
form 5 covalent bonds and form compounds, such as MX5.)
8
Chem 1B
Chapter 20 Exercises with Answers
5.
Draw the Lewis (electron-dots) structures for NCl3, PCl3 and PCl5. Predict the molecular geometry of
each compound. (NCl3 and PCl3 are trigonal pyramidal; PCl5 is trigonal bipyramidal)
6.
Ammonia is produce according to the following equation:
N2(g) + 3 H2(g)  2 NH3(g);
Ho = -92 kJ
(a) Does the formation of ammonia favor high temperature or low temperature? Explain.
(b) Does the formation of ammonia favor high pressure of low pressure? Explain.
(c) Industrial production of ammonia is normally carried out at temperature 250 – 300oC and pressure
150 – 200 atm. Discuss the advantage and disadvantage of carrying out the reaction under this industrial
setting.
(a) Reaction favors low temperature because heat is a product – increasing the temperature (by adding
heat) will shift the equilibrium to the left;
(b) Reaction favors high pressure because there are less gas molecules in the product; as reaction
progresses, the pressure will drop. Increasing the pressure shifts the equilibrium towards product.
(c) Carrying out the reaction at high temperature will speed up the reaction, but will reduce the yield at
equilibrium. The high pressure condition will force the equilibrium to the right and compensate the yield
lost by the high temperature condition.
7.
The Oswald process for the production of nitric acid involves the following reactions:
(i) 4NH3(g) + 5 O2(g)  4 NO(g) + 6H2O(g);
(ii) 2 NO(g) + O2(g)  2 NO2(g);
(iii) 3 NO2(g) + H2O(l)  2 HNO3(l) + NO(g);
(a) Calculate the enthalpy change (H, in kJ) for each reaction.
(b) Balance the following equation and calculate the overall enthalpy change for the reaction.
__NH3(g) + ___O2(g) + ___H2O(l)  ___HNO3(l) + ___NO(g) + ___H2O(g)
(c) How many kilograms of HNO3 are produced from 1.00 kg of NH3 ? (Assume 100% yield)
(d) If concentrated nitric acid is 16 M and its density is 1.48 g/mL, how many liters of concentrated
HNO3 can be produced from 1.00 kg of ammonia? (Assume 100% yield)
(Answer: (a) (i) -905 kJ; (ii) -113 kJ; (iii) -74 kJ; (c) 2.47 kg; (d) 2.45 L)
8.
Phosphorus is produced from phosphate rocks using the following equation:
2Ca3(PO4)2(s) + 6SiO2(s) + 10C(s)  P4(g) + 10CO(g) + 6CaSiO3(s)
How many kilograms of phosphorus can be produced from 1.00 metric tonne of Ca3(PO4)2 if the yield is
92.5%? (1 metric tonne = 1000 kg)
(Answer: 185 kg)
9
Chem 1B
Chapter 20 Exercises with Answers
9.
Write a balanced equation for the reaction between white phosphorus and an excess of oxygen gas and
for the reaction between tetraphosphorus decoxide with water. Give THREE major uses of phosphoric
acid.
P4(s) + 5 O2(g)  P4O10(s);
P4O10(s) + 6H2O(l)  4H3PO4(aq);
(Uses of phosphoric acid: (1) manufacture phosphate fertilizers; (2) manufacture of phosphate compounds
such as KH2PO4 and K2HPO4 for preparation of phosphate buffer; (3) manufacture of sodium phosphate
compounds (Na3PO4 as paint remover and oven cleaner; Na5P3O10 as water softener; (4) rust remover; (5)
as an additive in soft drinks such as colas.)
10.
Phosphoric acid is a triprotic acid, whereas phosphorous acid is a diprotic acid. Draw their Lewis
structures consistent with their acidic property.
Exercise #6:
1.
Name three major elements in the atmosphere and describe briefly their extraction process from the
atmosphere. There is more oxygen (by mass) in the ocean than in the atmosphere. Why oxygen is
commercially obtained from the atmosphere and not from the ocean?
(Nitrogen, oxygen and argon. Gases are extracted by fractional distillation of liquefied air.
Extracting oxygen from seawater involves distillation of the water (to remove salts) and electrolysis. These
processes are energy intensive)
2.
Give two major industrial uses of oxygen gas:
(1) An oxidizing agent for manufacture of various oxide of metals and nonmetals;
(2) Smelting of iron ore into steel; (3) reaction with ethylene to form ethylene oxide, which is then converted
to ethylene glycol (an antifreeze substance); (4) an oxidizer in rocket fuel; (5) metal cutting and welding;
3.
Write Lewis structures for O2 and O3 molecules.
4.
What is Frasch process? Briefly describe how this process works.
(Frasch process is used for the extraction of sulfur from sulfur deposit. Three concentric-ring pipes are
drilled into the sulfur bed. Superheated steam (~150 oC) is pumped down the outer ring to melt the sulfur and
high pressured hot air is pumped though the inner ring. The pressure from the steam and hot air force the
molten sulfur up the middle pipe.)
5.
Draw Lewis (electron-dots) structures for the following molecules:
(a) SO2
6.
(b) SF4
(c) SF6
(d) SO42-
(e) H2S2O7
Balance the following equations:
18 H2S(g) + 11 O2(g)  2 S8(s) + 2 SO2(g) + 18 H2O(g)
16 H2S(g) +
___S8(s) +
8 SO2(g)  3 S8(g) +
8 O2(g) 
16 H2O(g);
8 SO2(g)
2 SO2(g) + __O2(g)  2 SO3(g)
___SO3(g) + __H2O(l)  H2SO4(aq)
10
Chem 1B
Chapter 20 Exercises with Answers
7.
Give three major industrial uses of sulfuric acid, one use of Na2S2O3, and one use of SF6.
(1) manufacture of fertilizer ((NH4)2SO4), soap and detergents; (2) manufacture of phosphoric acid; (3)
manufacture of Al2(SO4)3; (4) manufacture of ethylene from ethanol; (5) dehydrating agents in sugar refinery.
8.
Balance the following equation:
__Ca5(PO4)3F(s) + 5 H2SO4(aq) + 10 H2O(l)  3 H3PO4(aq) + __HF(aq) + 5 CaSO4.2H2O(s)
(a) Using the balanced equation, calculate the volume, in liters, of concentrated sulfuric acid that will be
needed to react with 1.00 metric tonne of Ca5(PO4)3F? (b) How many liters of concentrated phosphoric
acid are produced? (1 metric ton = 1000 kg; concentrated H2SO4 has density = 1.84 g/mL and is 98.0%
(by mass) in H2SO4; concentrated H3PO4 has density = 1.685 g/mL and is 85.0% (by mass) in H2PO4.)
(Answer: (a) 539 L of concentrated H2SO4; (b) 242 L of 85% H3PO4)
9.
Write a balanced equation for the laboratory preparation of chlorine gas using manganese(IV) oxide and
sodium chloride in the presence of sulfuric acid.
( 2 NaCl(s) + MnO2(s) + 2 H2SO4(aq)  Cl2(g) + Na2SO4(aq) + MnSO4(aq) + 2 H2O(l))
10.
Balance the following redox reactions in basic solution:
(a) __Cl2(g) +
2 NaOH(aq)  NaOCl(aq) + __NaCl(aq) + __H2O(l)
(b) 3 Cl2(g) + 6 NaOH(aq)  NaClO3(aq) + 5 NaCl(aq) + 3 H2O(l)
11.
Write Lewis structures for the following oxo-acids of chlorine and rank the strength of these acids.
(a) HOCl
12.
(b) HOClO
(c) HOClO2
(d) HOClO3
(a) Balance the following equation for the reaction between aluminum and ammonium perchlorate:
( 10 Al(s) +
6 NH4ClO4(s) 
4 Al2O3(s) + 2 AlCl3(s) + 3 N2(g) + 12 H2O(g); Ho = ?
(b) How many kilograms of aluminum will react with 750 metric tons (7.5 x 105 kg) of ammonium
perchlorate. (Assume 100% efficient)
(c) Given the following thermodynamics data:
Compounds:
NH4ClO
Al2O3
AlCl3
H2O(g)
Hof (kJ/mol):
-295
-1676
-704
-242
Calculate the enthalpy change for the above reaction (after it is balanced)
(Answer: (b) 2.9 x 105 kg; (b) Ho = -9246 kJ)
13.
Draw the Lewis structures for the following molecules, predict their molecular shapes, and indicate
whether polar or nonpolar.
(a) XeF2
(b) XeF4
(c) XeO2F2
(d) XeO3F2
(e) XeO2F4
(f) XeOF4
11