Transcript Slide 1

1.
1 Mg, 2 O, and 2 H
2.
2 Mg, 2 O, and 2 H
3.
6 Mg, 6 O, and 6 H
4.
3 Mg, 6 O, and 6 H
1.
1 Mg, 2 O, and 2 H
2.
2 Mg, 2 O, and 2 H
3.
6 Mg, 6 O, and 6 H
4.
3 Mg, 6 O, and 6 H
1.
2.
3.
4.
NaS
NaS2
Na2S
Na2S2
1.
2.
3.
4.
NaS
NaS2
Na2S
Na2S2
1.
2.
3.
4.
too few significant figures are used in the problem’s
calculations.
there are experimental uncertainties in the
measurements.
coefficients are always rounded to integers so it doesn’t
matter.
approximations were made in the calculations.
1.
2.
3.
4.
too few significant figures are used in the problem’s
calculations.
there are experimental uncertainties in the
measurements.
coefficients are always rounded to integers so it doesn’t
matter.
approximations were made in the calculations.
1. 1.57 mol H2 reacts.
2. 0.785 mol H2 reacts.
3. Cannot be determined without more
information.
4. 3.14 mol H2 reacts.
1. 1.57 mol H2 reacts.
2. 0.785 mol H2 reacts.
3. Cannot be determined without more
information.
4. 3.14 mol H2 reacts.
The following equation is unbalanced:
CS2 + O2
CO2 + SO2
What is the correct balanced equation?
1. CS2 + 2 O2
→
CO2 + 2 SO2
2. 2 CS2 + 12 O2 → 2 CO2 + 4 SO2
3. CS2 + 3 O2 → CO2 + 2 SO2
4. CS2 + 6 O2 → CO2 + 2 SO2
Correct Answer:
1. CS2 + 2 O2
→
CO2 + 2 SO2
2. 2 CS2 + 12 O2 → 2 CO2 + 4 SO2
3. CS2 + 3 O2 → CO2 + 2 SO2
4. CS2 + 6 O2 → CO2 + 2 SO2
This is the only case where the number of each type of
atom is the same on both the reactant and product
sides of the equation.
Which of the following is the correct,
balanced chemical equation for the
combustion of ethanol (C2H5OH)?
1. C2H5OH + O2 → CO2 + H2O
2. C2H5OH + 3 O2 → 2 CO2 + 3 H2O
3. C2H5OH + 6 O2 → 4 CO2 + 6 H2O
4. 2 C2H5OH + 7 O2 → 4 CO
O 2 + 6 H 2O
O
C
C
O
Correct Answer:
1. C2H5OH + O2 → CO2 + H2O
2. C2H5OH + 3 O2 → 2 CO2 + 3 H2O
3. C2H5OH + 6 O2 → 4 CO2 + 6 H2O
4. 2 C2H5OH + 7 O2 → 4 CO2 + 6 H2O
OO
O
C
C
O
If the empirical formula of a compound is
C2H2N but the molecular weight is
160 g/mol, what is the molecular
formula?
1. C2H2N
2. C4H4N2
3. C6H8N3
4. C8H8N4
5. None of the above choices is correct.
Correct Answer:
1. C2H2N
2. C4H4N2
3. C6H8N3
4. C8H8N4
5. None of the above choices is correct.
FW C2H2N = (24 + 2 + 14) g/mol = 40 g/mol
MW/FW = 160/40 = 4
Thus, molecular formula is 4 empirical formula 4(C2H2N) =
C8H8N4
How many fluorine atoms are present in
2.0 moles of AlF3?
1. 3.0  1023
2. 6.0  1023
3. 1.2  1024
4. 3.6  1024
5. None of the above answers is correct.
Correct Answer:
1. 3.0  1023
2. 6.0  1023
3. 1.2  1024
4. 3.6  1024
5. None of the above answers is correct.
(2.0 moles AlF3)(6.0  1023 molecules
AlF3/mole AlF3) (3 atoms F/1 molecule AlF3)
= 3.6  1024
Which of the following samples has
the largest number of atoms?
1. 28 g Si
2. 28 g CO
3. 28 g N2
4. 15 g C2H4
5. All of the above have equal numbers of
atoms.
Correct Answer:
1. 28 g Si
2. 28 g CO
3. 28 g N2
4. 15 g C2H4
5. All of the
above have
equal numbers
of atoms.
28 g Si has 1 mole of
atoms, whereas 28 g of CO
and N2 have 2 moles of
atoms, even though they
also have only 1 mole
substance. However, there
are 6 atoms for every 1
mole of C2H4, so in this
case there are slightly
more than 3 moles worth
of atoms.
The molecular mass for the compound,
XClO3, is 122.5 amu. The atomic mass of
X is equal to ____ amu, which is the
element ____.
1. 1.0; H
2. 6.9; Li
3. 23.0; Na
4. 39.1; K
5. 85.5; Rb
Correct Answer:
1. 1.0; H
2. 6.9; Li
3. 23.0; Na
4. 39.1; K
5. 85.5; Rb
MW = 122.5 amu = AW X + AW Cl + 3(AW O)
122.5 amu  AW Cl  3 (AW O) = AW X
122.5 amu  (35.45 amu)  3 (16.0 amu) = AW X
122.5  35.45 amu  48.0 amu = AW X
AW X = 39.1 amu
When the chemical equation,
C4H10(g) + O2(g)
H2O(g) + CO2(g),
is balanced, the stoichiometric coefficients
are, respectively:
1. 1, 4, 5, 4
2. 2, 13, 10, 8
3. 2, 9, 8, 10
4. 2, 7, 4, 5
Correct Answer:
1. 1, 4, 5, 4
2. 2, 13, 10, 8
3. 2, 9, 8, 10
4. 2, 7, 4, 5
The combustion of methane (CH4) is shown
below:
CH4(g) + 2 O2(g)
2 H2O(l) + CO2(g)
How many grams of water are produced in the
combustion of 1.0 moles of methane?
1. 16 g
2. 32 g
3. 36 g
4. 48 g
Correct Answer:
1. 16 g
2. 32 g
3. 36 g
4. 48 g
(1.0 mole CH4)(2 moles H2O/1 mole CH4)(18 g H2O/1 mole H2O)
= 36 g
0.5 mol of carbon is combusted with 1.0 mol of
oxygen gas. Which of the following statements
is correct?
1. There is a molar excess of carbon, not
all carbon is consumed.
2. There is a molar excess of oxygen, not
all oxygen is consumed.
3. There are stoichiometrically equivalent
amounts of carbon and oxygen gas.
Correct Answer:
1. There is a molar excess of carbon, not
all carbon is consumed.
2. There is a molar excess of oxygen, not
all oxygen is consumed.
3. There are stoichiometrically equivalent
amounts of carbon and oxygen gas.
C and O2 react in a 1:1 stoichiometric
ratio, therefore there must be excess O2
because there was a larger initial
number of moles of it.
0.5 mol of carbon is combusted with
1.0 mol g of oxygen gas. How many
moles of carbon dioxide are produced?
1. 1.5 mol
2. 1.0 mol
3. 0.5 mol
4. 2.0 mol
Correct Answer:
1. 1.5 mol
2. 1.0 mol
3. 0.5 mol
4. 2.0 mol
C and O2 react in a 1:1 stoichiometric
ratio, therefore C must be the limiting
reagent and O2 must be the excess
reagent. Initially,
(0.5 moles C)(1 mole CO2/1 mole C) = 0.5
mole CO2
24.0 g of carbon are combusted with
32.0 g of oxygen gas. How many grams
of carbon dioxide are produced?
1. 56.0 g
2. 88.0 g
3. 28.0 g
4. 44.0 g
Correct Answer:
1. 56.0 g
2. 88.0 g
3. 28.0 g
4. 44.0 g
C and O2 react in a 1:1 stoichiometric ratio.
Initially,
(24.0 g C)  (1 mole C/12.0 g C)  (1 mole CO2/1
mole C) = 2.0 mole CO2
(32.0 g O2)  (1 mole O2/32.0 g O2)  (1 mole CO2/1
mole O2) = 1.0 mole CO2
Thus, O2 is limiting, and 1.0 mole of CO2 is 44.0 g.
3.0 moles Mg are combusted with 2.0
moles O2. What is the limiting reagent
and how many moles of the excess
reagent remain?
1.
2.
3.
4.
Magnesium, 0.5 mole
Magnesium, 1.0 mole
Oxygen gas, 0.5 mole
Oxygen gas, 1.0 mole
Correct Answer:
1.
2.
3.
4.
Magnesium, 0.5 mole
Magnesium, 1.0 mole
Oxygen gas, 0.5 mole
Oxygen gas, 1.0 mole
Mg and O2 react in a 2:1 stoichiometric ratio.
Initially,
(3 mole Mg)(2 mole MgO/2 mole Mg)
= 1.5 mole MgO
(2 mole O2)(2 mole MgO/1 mole O2) = 4 mole MgO
Thus, Mg is limiting, and 3 mol Mg will consume 1.5
mol of O2, leaving 0.5 mole of O2.
How many oxygen atoms are present
in MgSO4 • 7 H2O?
A.
B.
C.
D.
E.
4 oxygen atoms
5 oxygen atoms
7 oxygen atoms
11 oxygen atoms
18 oxygen atoms
How many oxygen atoms are present
in MgSO4 • 7 H2O?
A.
B.
C.
D.
E.
4 oxygen atoms
5 oxygen atoms
7 oxygen atoms
11 oxygen atoms
18 oxygen atoms
How many sulfur atoms are present
in 1.0 mole of Al2(SO4)3?
A.
B.
C.
D.
E.
1 sulfur atom
3 sulfur atoms
4 sulfur atoms
6.0 x 1023 sulfur atoms
1.8 x 1024 sulfur atoms
How many sulfur atoms are present
in 1.0 mole of Al2(SO4)3?
A.
B.
C.
D.
E.
1 sulfur atom
3 sulfur atoms
4 sulfur atoms
6.0 x 1023 sulfur atoms
1.8 x 1024 sulfur atoms
If you have equal masses of the
following metals, which will have the
most number of atoms?
A.
B.
C.
D.
E.
Lithium
Sodium
Potassium
Rubidium
Calcium
An alkali metal
Ca in H2O
If you have equal masses of the
following metals, which will have the
most number of atoms?
A.
B.
C.
D.
E.
Lithium
Sodium
Potassium
Rubidium
Calcium
An alkali metal
Ca in H2O
How many moles of oxygen gas are required
to react completely with 1.0 mole NO?
2 NO (g)
A.
B.
C.
D.
E.
0.5 mol O2
1.0 mol O2
1.5 mol O2
2.0 mol O2
2.5 mol O2
+
O2 (g)
2 NO2 (g)
How many moles of oxygen gas are required
to react completely with 1.0 mole NO?
2 NO (g)
A.
B.
C.
D.
E.
0.5 mol O2
1.0 mol O2
1.5 mol O2
2.0 mol O2
2.5 mol O2
+
O2 (g)
2 NO2 (g)
If 10.0 moles of NO are reacted with 6.0
moles O2, how many moles NO2 are
produced?
2 NO (g)
A.
B.
C.
D.
E.
+
O2 (g)
2.0 mol NO2
6.0 mol NO2
10.0 mol NO2
16.0 mol NO2
32.0 mol NO2
2 NO2 (g)
If 10.0 moles of NO are reacted with 6.0
moles O2, how many moles NO2 are
produced?
2 NO (g)
1.
2.
3.
4.
5.
+
2.0 mol NO2
6.0 mol NO2
10.0 mol NO2
16.0 mol NO2
32.0 mol NO2
O2 (g)
2 NO2 (g)
If you have equal concentrations of the
following aqueous solutions, which
will have the highest conductivity?
A.
B.
C.
D.
E.
CaCl2
KBr
Na2SO4
Al(NO3)3
LiC2H3O2
If you have equal concentrations of the
following aqueous solutions, which
will have the highest conductivity?
A.
B.
C.
D.
E.
CaCl2
KBr
Na2SO4
Al(NO3)3
LiC2H3O2
Which mixture will produce a
precipitate?
1.
NH
2.
HClO
3.
Na SO
4.
Ca(NO
5.
(NH
3
+
HF
+
KOH
4
2
4
)
3 2
) CO
4 2
3
+
PbCl
+
KC
+ Na
2
2
3
H O
3
PO
4
2
Which mixture will produce a
precipitate?
1.
NH
2.
HClO
3.
Na SO
4.
Ca(NO
5.
(NH
3
+
HF
+
KOH
4
2
4
)
3 2
) CO
4 2
3
+
PbCl
+
KC
+ Na
2
2
3
H O
3
PO
4
2
What is(are) the spectator ion(s) in the
following reaction?
KOH (aq) + HF (aq)
A.
B.
C.
D.
E.
K+
FK+ and FOH- and H+
OH-
KF (aq) + H2O (l)
What is(are) the spectator ion(s) in the
following reaction?
KOH (aq) + HF (aq)
A.
B.
C.
D.
E.
K+
FK+ and FOH- and H+
OH-
KF (aq) + H2O (l)
Which of the following reactions has
the net ionic equation:
H+ (aq)
A.
B.
C.
D.
E.
Reaction 1
Reactions 1, 4
Reactions 2, 3
Reactions 2, 4
Reactions 3, 4
+
OH- (aq)
1)
2)
3)
4)
HClO 4
HF
H3PO4
H2SO4
H2O (l)
+
+
+
+
KOH
NaOH
KOH
Ca(OH) 2
Which of the following reactions has
the net ionic equation:
H+ (aq)
A.
B.
C.
D.
E.
+
Reaction 1
Reactions 1, 4
Reactions 2, 3
Reactions 2, 4
Reactions 3, 4
OH- (aq)
1)
2)
3)
4)
H2O (l)
HClO 4
HF
H3PO4
H2SO4
+
+
+
+
KOH
NaOH
KOH
Ca(OH) 2
Which will have the highest
concentration of Na+?
A.
B.
C.
D.
E.
0.35 M Na2SO4
0.40 M Na3PO4
0.50 M NaNO3
0.80 M NaOH
1.00 M NaCl
Which will have the highest
concentration of Na+?
A.
B.
C.
D.
E.
0.35 M Na2SO4
0.40 M Na3PO4
0.50 M NaNO3
0.80 M NaOH
1.00 M NaCl
Given the following reactions, rank
the activity of each metal.
2 Al + 3 ZnCl 2  2 AlCl 3 + 3 Zn
3 Mg + 2 AlCl 3 3 MgCl2 + 2 Al
Zn + CuCl 2
A.
B.
C.
D.
E.
ZnCl 2 + Cu
Mg>Al>Zn>Cu
Al>Mg>Zn>Cu
Cu>Zn>Al>Mg
Zn>Cu>Al>Mg
Al>Mg>Cu>Zn
Given the following reactions, rank
the activity of each metal.
2 Al + 3 ZnCl 2  2 AlCl 3 + 3 Zn
3 Mg + 2 AlCl 3 3 MgCl2 + 2 Al
Zn + CuCl 2
A.
B.
C.
D.
E.
ZnCl 2 + Cu
Mg>Al>Zn>Cu
Al>Mg>Zn>Cu
Cu>Zn>Al>Mg
Zn>Cu>Al>Mg
Al>Mg>Cu>Zn
Which of the following substances
would be considered a nonelectrolyte?
1. Methanol, CH3OH
2. Hydrofluoric acid, HF
3. Sulfuric acid, H2SO4
4. Sodium hydroxide,
NaOH
Correct Answer:
1. Methanol, CH3OH
2. Hydrofluoric acid, HF
3. Sulfuric acid, H2SO4
4. Sodium hydroxide,
NaOH
Methanol is an organic molecule
that does not form ions in solution.
Which ions are spectator ions in the
reaction represented by the following
molecular equation?
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
1. Na+ and NO3
2. Na+ and Cl
3. Ag+ and Cl
4. Ag+ and NO3
Correct Answer:
1. Na+ and NO3
2. Na+ and Cl
3. Ag+ and Cl
4. Ag+ and NO3
Spectator ions are present, but play
no direct role in the reaction.
Which of the following
is not an oxidationreduction reaction?
1. CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g)
2. HCl(aq) + Zn(s)  ZnCl2(aq) + H2(g)
3. Ca(OH)2(aq) + 2 HCl(aq)  CaCl2(aq) + 2 H2O(l)
4. Fe2O3(s) + 3 H2(g)  2 Fe(s) + 3 H2O(l)
Correct Answer:
1. CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g)
2. HCl(aq) + Zn(s)  ZnCl2(aq) + H2(g)
3. Ca(OH)2(aq) + 2 HCl(aq)  CaCl2(aq) + 2 H2O(l)
4. Fe2O3(s) + 3 H2(g)  2 Fe(s) + 3 H2O(l)
This is an acid-base
reaction, and no species
change oxidation state.
What is the oxidation state of sulfur in
the compound SF2?
1. 0
2. +2
3. +4
4.
2
5.
4
Correct Answer:
1. 0
2. +2
3. +4
4.
2
5.
4
Because F is 1, and there are two F atoms, S
must be +2.
What is the oxidation state of nitrogen in
the compound N2O5?
1. 0
2. +1
3. +2
4. +5
5.
3
Correct Answer:
1. 0
2. +1
3. +2
4. +5
5.
3
Because O is 2, and there are five O atoms,
each of the two N atoms must be +5.
Which of the following compounds
contains a chlorine atom with an
oxidation number of +5?
1. ClF5
2. KClO4
3. HCl
4. Cl2
Correct Answer:
1. ClF5
2. KClO4
3. HCl
4. Cl2
Because F is 1, and
there are five F
atoms, the Cl atom
must be +5.
Structure of ClF5 is
to the left.
A 80.0 mL solution of sodium chloride at
1.00 M is to be diluted to 0.100 M. What
is the total volume of the diluted
solution?
1. 0.0720 L
2. 0.720 L
3. 0.0800 L
4. 0.800 L
MdiluteVdilute = moles = MconcVconc
Correct Answer:
1. 0.0720 L
2. 0.720 L
3. 0.0800 L
4. 0.800 L
0.100 M(Vdilute) = (1.00 M)(80.0 mL)
Vdilute = (1.00 M)(80.0 mL)/0.100 M
Vdilute = 800. mL, or 0.800 L
How many moles of phosphoric acid,
H3PO4, are needed to prepare 2.00 L of a
0.75 M phosphoric acid solution?
1. 4.0 moles
2. 1.5 moles
3. 1.8 moles
4. 0.75 moles
Molarity 
moles of solute
v olume of solution in liters
How many moles of phosphoric acid,
H3PO4, are needed to prepare 2.00 L of a
0.75 M phosphoric acid solution?
1. 4.0 moles
2. 1.5 moles
3. 1.8 moles
4. 0.75 moles
Molarity 
moles of solute
v olume of solution in liters
A 50.0 mL solution of HCl at 1.00 M is to be
titrated with a solution of 2.50 M NaOH. How
many mL of NaOH are required to reach the
equivalence point?
1. 20.0 mL
2. 125 mL
3. 50.0 mL
4. 70.0 mL
Correct Answer:
1. 20.0 mL
3. 50.0 mL
2. 125 mL
4. 70.0 mL
(50.0 mL HCl)(1.00 M) = 0.0500 mol acid
0.0500 mol acid(1 mol base/1 mol acid)
= 0.100 mol base
Vbase = mol/M = 0.100 mol/2.50M
= 0.0200 L or 20.0 mL
A 50.0 mL solution of H2SO4 at 1.00 M is to be
titrated with a solution of 0.500 M NaOH. How
many mL of NaOH are required to reach the
equivalence point?
1. 100. mL
2. 200. mL
3. 300. mL
4. 50.0 mL
Correct Answer:
1. 100. mL
2. 200. mL
3. 300. mL
4. 50.0 mL
(50.0 mL H2SO4)(1.00 M) = 0.0500 mol acid
0.0500 mol acid(2 mol base/1 mol acid)
= 0.100 mol base
Vbase = mol/M = 0.100 mol/0.500M
= 0.200 L or 200. mL
1. KCN(aq)
2. K+(aq) and CN–(aq)
3. K–(aq) and CN+(aq)
4. K+(aq), C4–(aq), and N3+(aq)
1. KCN(aq)
2. K+(aq) and CN–(aq)
3. K–(aq) and CN+(aq)
4. K+(aq), C4–(aq), and N3+(aq)
1. NaClO4(aq)
2. Na+(aq) and 4ClO–(aq)
3. Na+(aq), Cl–(aq) and 4O2–(aq)
4. Na+(aq) and ClO4–(aq)
1. NaClO4(aq)
2. Na+(aq) and 4ClO–(aq)
3. Na+(aq), Cl–(aq) and 4O2–(aq)
4. Na+(aq) and ClO4–(aq)
1. Cannot determine
without concentration
information.
2. Both will cause the
lightbulb to glow with
equal brightness.
3. MgBr2
4. CH3OH
1. Cannot determine without concentration
information.
2. Both will cause the lightbulb to glow with
equal brightness.
3. MgBr2
4. CH3OH
1. Cannot determine without concentration
information.
2. HBr
3. H2SO3
4. HC2H3O2
1. Cannot determine without concentration
information.
2. HBr
3. H2SO3
4. HC2H3O2
1.
2.
3.
4.
Concentration (molarity) remains the same.
The new concentration is 0.25 M.
The new concentration is 1.00 M.
The new concentration is 2.00 M.
1.
2.
3.
4.
Concentration (molarity) remains the same.
The new concentration is 0.25 M.
The new concentration is 1.00 M.
The new concentration is 2.00 M.
1.
2.
3.
4.
12.50 mL
25.00 mL
50.00 mL
75.00 mL
1.
2.
3.
4.
12.50 mL
25.00 mL
50.00 mL
75.00 mL