CHEM 120 WEEK 8 FINAL EXAM 2 LATEST VERSIONS ACTUAL EXAM 250
QUESTIONS AND CORRECT DETAILED ANSWERS WITH RATIONALES
(VERIFIED ANSWERS) |ALREADY GRADED A+
How many bonds can nitrogen have? Which rule or principle should be used?
A) Five bonds; octet rule.
B) Three bonds; octet rule.
C) Three bonds; the Hund's rule.
D) Five bonds; the Aufbau Principle. - ANSWER: B
When two hydrogen atoms meet, they will attract to each other and form a bond
(and a H2 molecule). Why?
A) Because electrons like to stay together.
B) Because electrons like to be paired up.
C) Because there is attraction between the electron in one hydrogen atom and the
nucleus of another hydrogen atom.
D) Gravitational attraction between two atoms binds two hydrogen atoms (or any
two atoms) together into a molecule. - ANSWER: C
How do you determine the number of electron domains on the central atom?
A) Draw Lewis structure of the compound, then add up the numbers of lone electron
pair, single bond, double bond, and triple bond.
B) The # of electron domains = the # of valence electrons
C) The # of electron domains = the number of atoms the central atom is bonded to.
D) The # of electron domains = the # of valence electrons divided by 2 - ANSWER: A
Indicate partial charges on each atom of the following two bonds: C-Br and O-N.
A) Carbon has partial negative charge and bromine has partial positive charge; both
oxygen and nitrogen have no charge.
B) Carbon has partial positive charge and bromine has partial negative charge;
oxygen has partial negative charge and nitrogen has partial positive charge.
C) Carbon has partial negative charge and bromine has partial positive charge;
oxygen has partial positive charge and nitrogen has partial negative charge.
D) Carbon has partial positive charge and bromine has partial negative charge;
oxygen has partial positive charge and nitrogen has partial negative charge. -
ANSWER: B
In which of the above structures, the nitrogen atom carries a negative formal
charge?
A) a
B) b
C) c
,D) d - ANSWER: A
In which of the above Lewis structures, the oxygen atom carries a positive formal
charge?
A) a
B) b,c
C) a,d
D) c
E) d - ANSWER: B
Which of the following compounds exists?
A) CH3CH3CH3
B) (CH3) 2CCH3
C) CH3CHCH2CH3
D) (CH3)2CHCH3 - ANSWER: D
Indicate hybridization of oxygen atom in the following compounds:
H2O, H2C=O, H3O+, HO-, and CO
A) sp3, sp3, sp3, sp3, sp B) sp3, sp2, sp2, sp, sp
C) sp3, sp2, sp3, sp3, sp D) sp, sp2, sp2, sp, sp - ANSWER: C
Indicate hybridization of carbon in the above compounds.
A) sp3, sp2, sp3, sp2
B) sp3, sp2, sp2, sp2
C) sp3, sp3, sp3, sp2
D) sp3, sp3, sp3, sp3 - ANSWER: A
What is the bond angle in a perfect tetrahedron molecule like CH4?
A) 120
B) 0
C) 180
D) 109.5 - ANSWER: D
When SO3 reacts water, sulfuric acid (H2SO4) is formed. Is SO3 a BrØnsted-Lowry
acid?
A) No, it is not a BrØnsted-Lowry acid.
B) Yes, it is a BrØnsted-Lowry acid. - ANSWER: A
Conjugate acid and base is a concept unique to BrØnsted-Lowry acids and bases.
Which of the pairs below are not conjugate acid and base?
a. H2SO4 and SO42- b. H2CO3, CO2 c. HCl and Cl2 d. H3O+ and HO- e. HBr and Br-
A) a,b,c B) a,b,c,d C) a,b D) a,b,c,d,e E) e - ANSWER: B
, What is the pH value of an acidic solution with a proton molar concentration of 10^-
3?
A) 0.001 B) 0.003 C) 3 D) -3 - ANSWER: C
Gastric acid is composed of hydrochloric acid (HCl) - a strong acid. The pH range of
gastric acid is 1.5 to 3.5 in the human stomach. If the HCl concentration is 0.5
mole/liter in John's stomach, is the pH value of his gastric acid in the normal range,
too high, or too low?
A) Too low B) Too high C) In the normal range. - ANSWER: A
Which of the compounds below is the smallest carboxylic acid? (Some carboxylic
acids can found in Section 2.3) 58%
A) Methyl alcohol (MeOH)
B) Methylamine (CH3NH2)
C) Acetic acid
D) Formic acid - ANSWER: D
Hydronium (H3O+) has a pKa of -1.7, and is the strongest acid that can exist in water.
A carboxylic acid (RCOOH) can be protonated by hydronium. So, the pKa of RCOOH:
A) must be greater than -1.7
B) cannot be determined
C) must be smaller than -1.7 - ANSWER: A
What is the molecular formula of carbonic acid? Is it a strong acid? (Section 2.2)
A) H2CO3. It is a very weak acid.
B) H2CO3. It is a weak acid.
C) HCO3. It is a very weak acid.
D) CO2. It is a moderately strong acid. - ANSWER: A
Hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and acetic acid
(CH3COOH) are the most commonly used acids. Find their pKa values in sections 2.2-
2.6 (or online) and determine which of the following sequences is in the order of
ascending acid strength.
A) CH3COOH < HNO3 < H2SO4 < HCl
B) CH3COOH < HNO3 < HCl < H2SO4
C) CH3COOH < HCl < H2SO4 < HNO3
D) HCl < H2SO4 < HNO3 < CH3COOH - ANSWER: A
If HB1 is a stronger BrØnsted-Lowry acid than HB2 (also a BrØnsted-Lowry acid),
which is more likely to be protonated when the two are mixed?
A) HB1
B) HB2
QUESTIONS AND CORRECT DETAILED ANSWERS WITH RATIONALES
(VERIFIED ANSWERS) |ALREADY GRADED A+
How many bonds can nitrogen have? Which rule or principle should be used?
A) Five bonds; octet rule.
B) Three bonds; octet rule.
C) Three bonds; the Hund's rule.
D) Five bonds; the Aufbau Principle. - ANSWER: B
When two hydrogen atoms meet, they will attract to each other and form a bond
(and a H2 molecule). Why?
A) Because electrons like to stay together.
B) Because electrons like to be paired up.
C) Because there is attraction between the electron in one hydrogen atom and the
nucleus of another hydrogen atom.
D) Gravitational attraction between two atoms binds two hydrogen atoms (or any
two atoms) together into a molecule. - ANSWER: C
How do you determine the number of electron domains on the central atom?
A) Draw Lewis structure of the compound, then add up the numbers of lone electron
pair, single bond, double bond, and triple bond.
B) The # of electron domains = the # of valence electrons
C) The # of electron domains = the number of atoms the central atom is bonded to.
D) The # of electron domains = the # of valence electrons divided by 2 - ANSWER: A
Indicate partial charges on each atom of the following two bonds: C-Br and O-N.
A) Carbon has partial negative charge and bromine has partial positive charge; both
oxygen and nitrogen have no charge.
B) Carbon has partial positive charge and bromine has partial negative charge;
oxygen has partial negative charge and nitrogen has partial positive charge.
C) Carbon has partial negative charge and bromine has partial positive charge;
oxygen has partial positive charge and nitrogen has partial negative charge.
D) Carbon has partial positive charge and bromine has partial negative charge;
oxygen has partial positive charge and nitrogen has partial negative charge. -
ANSWER: B
In which of the above structures, the nitrogen atom carries a negative formal
charge?
A) a
B) b
C) c
,D) d - ANSWER: A
In which of the above Lewis structures, the oxygen atom carries a positive formal
charge?
A) a
B) b,c
C) a,d
D) c
E) d - ANSWER: B
Which of the following compounds exists?
A) CH3CH3CH3
B) (CH3) 2CCH3
C) CH3CHCH2CH3
D) (CH3)2CHCH3 - ANSWER: D
Indicate hybridization of oxygen atom in the following compounds:
H2O, H2C=O, H3O+, HO-, and CO
A) sp3, sp3, sp3, sp3, sp B) sp3, sp2, sp2, sp, sp
C) sp3, sp2, sp3, sp3, sp D) sp, sp2, sp2, sp, sp - ANSWER: C
Indicate hybridization of carbon in the above compounds.
A) sp3, sp2, sp3, sp2
B) sp3, sp2, sp2, sp2
C) sp3, sp3, sp3, sp2
D) sp3, sp3, sp3, sp3 - ANSWER: A
What is the bond angle in a perfect tetrahedron molecule like CH4?
A) 120
B) 0
C) 180
D) 109.5 - ANSWER: D
When SO3 reacts water, sulfuric acid (H2SO4) is formed. Is SO3 a BrØnsted-Lowry
acid?
A) No, it is not a BrØnsted-Lowry acid.
B) Yes, it is a BrØnsted-Lowry acid. - ANSWER: A
Conjugate acid and base is a concept unique to BrØnsted-Lowry acids and bases.
Which of the pairs below are not conjugate acid and base?
a. H2SO4 and SO42- b. H2CO3, CO2 c. HCl and Cl2 d. H3O+ and HO- e. HBr and Br-
A) a,b,c B) a,b,c,d C) a,b D) a,b,c,d,e E) e - ANSWER: B
, What is the pH value of an acidic solution with a proton molar concentration of 10^-
3?
A) 0.001 B) 0.003 C) 3 D) -3 - ANSWER: C
Gastric acid is composed of hydrochloric acid (HCl) - a strong acid. The pH range of
gastric acid is 1.5 to 3.5 in the human stomach. If the HCl concentration is 0.5
mole/liter in John's stomach, is the pH value of his gastric acid in the normal range,
too high, or too low?
A) Too low B) Too high C) In the normal range. - ANSWER: A
Which of the compounds below is the smallest carboxylic acid? (Some carboxylic
acids can found in Section 2.3) 58%
A) Methyl alcohol (MeOH)
B) Methylamine (CH3NH2)
C) Acetic acid
D) Formic acid - ANSWER: D
Hydronium (H3O+) has a pKa of -1.7, and is the strongest acid that can exist in water.
A carboxylic acid (RCOOH) can be protonated by hydronium. So, the pKa of RCOOH:
A) must be greater than -1.7
B) cannot be determined
C) must be smaller than -1.7 - ANSWER: A
What is the molecular formula of carbonic acid? Is it a strong acid? (Section 2.2)
A) H2CO3. It is a very weak acid.
B) H2CO3. It is a weak acid.
C) HCO3. It is a very weak acid.
D) CO2. It is a moderately strong acid. - ANSWER: A
Hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and acetic acid
(CH3COOH) are the most commonly used acids. Find their pKa values in sections 2.2-
2.6 (or online) and determine which of the following sequences is in the order of
ascending acid strength.
A) CH3COOH < HNO3 < H2SO4 < HCl
B) CH3COOH < HNO3 < HCl < H2SO4
C) CH3COOH < HCl < H2SO4 < HNO3
D) HCl < H2SO4 < HNO3 < CH3COOH - ANSWER: A
If HB1 is a stronger BrØnsted-Lowry acid than HB2 (also a BrØnsted-Lowry acid),
which is more likely to be protonated when the two are mixed?
A) HB1
B) HB2
