Chem 110 Exam 2
What is the formal charge of an oxygen atom that forms three bonds and has one lone pair? -2 -1 0 +1 +2
+1
Which of these statements are true? (Select all that apply) - Lattice energy is the change in energy when an ionic solid is separated into isolated ions in the gas phase. - Ionic compounds are stable. - The formation of NaCl(s) from the elements requires a large input of energy. - Compounds are stable if it is difficult to break them into their component pieces - Lattice energy is highly exothermic.
- Lattice energy is the change in energy when an ionic solid is separated into isolated ions in the gas phase. - Ionic compounds are stable. - Compounds are stable if it is difficult to break them into their component pieces
Which of these statements apply to molecular compounds? (Select all that apply) They consist of positive and negative ions. They consist of individual molecules. They are usually a combination of a metal and nonmetal. They are composed of all nonmetals or nonmetals and metalloids. They usually have low melting points. They have high melting points and are brittle.
- They consist of individual molecules. - They are composed of all nonmetals or nonmetals and metalloids. - They usually have low melting points.
Which of these properties of ionic compounds are macroscopic properties (measurable experimental properties)? [Select all that apply.] - soluble only in polar solvents (i.e. water) - very high melting and boiling points - hard but brittle - distinct +/− ions"infinite" crystal lattice - strong omnidirectional electrostatic bond - slow electrical conductivity as solids
- soluble only in polar solvents (i.e. water) - very high melting and boiling points - hard but brittle - slow electrical conductivity as solids
The molecular formula of allicin is C6H10OS2. How many moles of S atoms are present in the 5g of allicin?
0.062 moles (2 S moles for every mole of allicin)
Draw the Lewis structure for HCN. How many bonds does the C-H bond contain? 4 2 3 1
1
Draw the Lewis structure for HCN. How many lone pairs does the N have? 4 2 3 1
1
The molecule below is responsible for the aroma of popcorn. What is the percentage by mass of nitrogen (N) in this compound? [C6H9NO]
12.6%
What is the molar mass of C6H8O4? Express your answer in units of grams per mole. Provide your answer to at least one decimal place.
144.124
What is the molar mass of C7H9O4? Express your answer in units of grams per mole. Provide your answer to at least one decimal place.
157.07
What is the percent of N in TNT? The molecular formula of TNT is C7H5N3O6.
18.5%
If molecule has no lone pairs and two identical bonded atoms: AX2, what X-A-X bond angle will minimize the repulsion between the bonds? 180° 109.5° 90° 90°, 120° 120°
180
How many valence electrons are there in the bromine tetrafuoride ion, BrF4-? 34 30 36 38 35 32
36
How many atoms are in the molecule C6H11O22?
39
How many moles of hydrogen atoms are in a 4.8 g sample of H2 gas? [Express your answer to at least one decimal place.]
4.8
What is the mass percentage of carbon in C6H12O3? Express your answer as a percentage (i.e., out of 100%), but do not write the percentage sign in your answer. Express your answer to at least one decimal place.
54.5
What is the mass percentage of carbon in C6H10O3? Express your answer as a percentage (i.e., out of 100%), but do not write the percentage sign in your answer. Express your answer to at least one decimal place.
55.4
90.1g of FeCl3 x nH2O is heated to drive off all of the water hydration. The mass of the remaining salt is 54.1g. What is the value of x in the formula for the hydrate?
6
How many atoms are in the substance MgSO4?
6
How many valence electrons are there in the ammonium ion NH4+? 7 8 6 5 9 10
8
How many valence electrons are there in the hydronium ion, H3O+? 9 4 8 7 2 6
8
How many moles of hydrogen atoms are in a 9.3 g sample of H2 gas? [Express your answer to at least one decimal place.]
9.3
Which molecules would be polar? [Select all that apply.] Group of answer choices A linear molecule with one polar bond and one nonpolar bond. A linear molecule with two equivalent polar bonds. A bent molecule with two equivalent polar bonds. A bent molecule with two nonpolar bonds. A bent molecule with one polar bond and one nonpolar bond. A linear molecule with two nonpolar bonds.
A linear molecule with one polar bond and one nonpolar bond A bent molecule with two equivalent polar bonds. A bent molecule with one polar bond and one nonpolar bond.
If there are extra electrons after completing the octets for all atoms in a molecule in the Lewis structure, what should you do with the extra electrons? Ignore them, assume you counted incorrectly. Use them to make extra double bonds. Add them as lone pairs to the central atom.
Add them as lone pairs to the central atom
A molecule with 5 electron domains has three lone pairs. What positions in the molecular geometry will the lone pairs occupy? One will go in an axial position, two in the equatorial plane. All three will go in the equatorial plane. The placement doesn't matter so it will vary randomly. Two will go in the axial positions, one in the equatorial plane.
All three will go in the equatorial plane
Which of the following atoms would have a formal charge of +1? An oxygen atom that forms three bonds and has one lone pair. A sulfur atom that forms four bonds and has one lone pair. A phosphorus atom that forms three bonds and has one lone pair. A sulfur atom that forms two bonds and has two lone pairs. A carbon atom that forms two double bonds. A nitrogen atom that forms two bonds and has two lone pairs. A nitrogen atom that forms four bonds and has no lone pairs.
An oxygen atom that forms three bonds and has one lone pair. A nitrogen atom that forms four bonds and has no lone pairs
Which atoms are likely to form stable molecules that have an incomplete octet on the central atom? [Select all that apply.] B C F H Be Si P
B and Be
The active ingredient in Benadryl is diphenhydramine. The percent composition by mass of diphenhydramine is 80.0% C, 8.28% H, 5.49%N, and 6.27% O. What is the empirical formula of diphenhydramine?
C17H21NO
Cholesterol is a molecule that contains C, H, O. If it is 83.87% C and 11.99% H by mass, what. is th eempirical formula of cholesterol?
C27H46O
formula for acitate
C2H3O2
Combustion of a 4.61g sample of an unknown alcohol (CxHyOz) produced 8.8g of CO2 and 5.4g of H2O. What is the empirical formula of the alcohol?
C2H5OH
The characteristic odor of pineapple is due to ethyl butyrate, a compound containing C, H, and O. COmbustion of 2.78mg of ethyl butyrate produces 6.32mg of CO2 and 2.58mg of H2O. What is the empirical formula of the compound?
C3H6O
A 50g sample of an unknown compound containing only C and H is completely combusted in air, yielding 64.3g of H2O. What is the empirical formula of the unknown compound?
CH2
Which of these is the correct formula for the hypochlorite ion? ClO- ClO2- ClO3- ClO4-
ClO-
Given the Lewis structure of a molecule, how do you determine the number of electron domains? [Select all that apply.] Each bonded atom counts as an electron domain. Each double bond counts as two electron domains. Each lone pair counts as an electron domain. Each triple bond counts as three electron domains.
Each bonded atom counts as an electron domain. Each lone pair counts as an electron domain.
Shown below is a bond between two elements, X and Y. The direction of the dipole moment is indicated. Which of the following statements are true? [Select all that apply.] -|---> X---Y Element Y carries a partial positive charge. Elements X and Y have the same electronegativity. Element X is more electronegative than element Y. Element X carries a partial negative charge. Element Y carries a partial negative charge. Element X carries no partial charge. Element Y carries no partial charge. Element Y is more electronegative than element X. Element X carries a partial positive charge.
Element Y is more electronegative than element X. Element X carries a partial positive charge. Element Y carries a partial negative charge.
Which of the following bonds would be classified as nonpolar covalent bonds? You may want to use Figure F07-2-2 in the e-book to help answer this question. [Select all that apply.] C-C C-F F-F P-H N-H C-H Li-Cl C-N
F-F P-H C-H C-C
What is the correct formula for determining formal charge (FC)? FC = NV − NLS FC = NLS − NV FC = ½ (NV − NLS) FC = ½ NV − NLS FC = ½ NLS − NV
FC = NV − NLS
Which statement best describes why covalent bonds form? Forming a bond releases energy. Forming a bond results in oppositely charged ions. Forming a bond allows a nonmetal to give up its electrons. Forming a bond allows electrons to be closer to each other. Forming a bond absorbs energy.
Forming a bond releases energy.
Match these words or phrases with their descriptions. Ionic bonding bonding Shared electrons metallic bonding - Valence electrons are shared among all atoms and electrons are able to move freely throughout the solid. -The attraction between ions of opposite charges lowers the energy of the system. - electrostatically attracted to the bonded nuclei, lowering the energy of the system. - Interactions between atoms result in a more stable system. covalent bonding
Ionic bonding = The attraction between ions of opposite charges lowers the energy of the system. bonding = Interactions between atoms result in a more stable system. covalent bonding = Shared electrons are electrostatically attracted to the bonded nuclei, lowering the energy of the system. metallic bonding = Valence electrons are shared among all atoms and electrons are able to move freely throughout the solid.
What molecular features are necessary for a molecule to be polar? [Select all that apply.] The bond dipoles have to be equal in strength and opposite in direction. It has to have a molecular geometry where the bond dipoles do not cancel. It must have polar bonds. It must have a symmetric molecular geometry.
It has to have a molecular geometry where the bond dipoles do not cancel. It must have polar bonds.
Which of the following are ionic compounds? [Select all that apply.] K3PO4 H3PO4 H2S MgCl2 NH3 NH4NO3 CH4
K3PO4 MgCl2 NH4NO3
What is the molecular geometry and electron geometry configuration and angle for AX2E0
Linear 180
Which compound will have the highest melting point? NaCl NaI MgO
MgO
What category of octet exception does this molecule belong to? [BH3] Molecules or polyatomic ions with an odd number of electrons Molecules or polyatomic ions with atoms that have fewer than an octet of valence electrons Molecules or polyatomic ions with atoms that have more than an octet of valence electrons This molecule does not violate the octet rule
Molecules or polyatomic ions with atoms that have fewer than an octet of valence electrons
What category of octet exception does this molecule belong to? [XeF4] Molecules or polyatomic ions with an odd number of electrons Molecules or polyatomic ions with atoms that have fewer than an octet of valence electrons This molecule does not violate the octet rule Molecules or polyatomic ions with atoms that have more than an octet of valence electrons
Molecules or polyatomic ions with atoms that have more than an octet of valence electrons
Which of these are examples of polyatomic molecules? NH3 HNO3 H2O H2 NO HCl
NH3 HNO3
Which compound would you expect to have the highest melting point? - H2S - NH3 - NaCl - HCl
NaCl
What is the molecular geometry and electron geometry configuration and angle for AX6E0
Octahedral 90, 180
What is the molecular geometry and electron geometry configuration and angle for AX4E2
Octahedral square planar 90, 180
What is the molecular geometry and electron geometry configuration and angle for AX5E1
Octahedral square pyramidal <90, <180
formula of phosphate
PO4 3-
Which statements about a sulfur-fluorine bond are true? [Select all that apply.] Sulfur carries a partial positive charge. Fluorine carries a partial positive charge. Sulfur carries a partial negative charge. Fluorine carries a partial negative charge. Neither atom will carry a partial charge. Sulfur is more electronegative than fluorine. Fluorine is more electronegative than sulfur.
Sulfur carries a partial positive charge. Fluorine carries a partial negative charge. Fluorine is more electronegative than sulfur.
What is the molecular geometry of a molecule with a steric number of 5 and 2 lone pairs? trigonal bipyramidal trigonal planar bent tetrahedral T-Shaped
T-Shaped
What is the molecular geometry and electron geometry configuration and angle for AX4E0
Tetrahedral 109.5
What is the molecular geometry and electron geometry configuration and angle for AX3E1
Tetrahedral Trigonal pyramidal <109.5
What is the molecular geometry and electron geometry configuration and angle for AX2E2
Tetrahedral bent <109.5
A free radical violates the octet rule because... The radical ions have disassociated The radical has an odd number of elections The radical contains more than eight electrons
The radical has an odd number of elections
A molecule with 6 electron domains has two lone pairs. What positions in the molecular geometry will the lone pairs occupy? They will be in positions that are on opposites sides of the molecule with 180° angle between them. They will be in a position that places them 90° apart in the molecule. The placement doesn't matter so it will vary randomly.
They will be in positions that are on opposites sides of the molecule with 180° angle between them.
What category of octet exception does this molecule belong to? [H2O] Molecules or polyatomic ions with an odd number of electrons Molecules or polyatomic ions with atoms that have fewer than an octet of valence electrons Molecules or polyatomic ions with atoms that have more than an octet of valence electrons This molecule does not violate the octet rule
This molecule does not violate the octet rule
What is the molecular geometry and electron geometry configuration and angle for AX5E0
Trigonal bipyramidal 90, 120, 180
What is the molecular geometry and electron geometry configuration and angle for AX3E2
Trigonal bipyramidal T-shape <90, <180
What is the molecular geometry and electron geometry configuration and angle for AX4E1
Trigonal bipyramidal seesaw <90, <120, <180
What is the molecular geometry and electron geometry configuration and angle for AX2E3
Trigonal bipyramidal linear 180
What is the molecular geometry and electron geometry configuration and angle for AX3E0
Trigonal planar 120
What is the molecular geometry and electron geometry configuration and angle for AX2E1
Trigonal planar bent <120
Which of these has the longest bond? a C-C single bond a C-C double bond a C-C triple bond
a C-C single bond
Which of these has the highest bond order? a C-C single bond a C-C double bond a C-C triple bond
a C-C triple bond
An electron being shared between two elements in a Lewis structure is part of a bonded pair couple electron sea lone pair
bonded pair
Match these words with their definition. covalent bond σ bonds π bonds hybridization bond dissociation energy the amount of energy needed to break apart a covalent bond the mixing of atomic orbitals to produce a set of equal number of hybrid orbitals an increase in the electron density between two nuclei the distance between the centers of the nuclei of two bonded atoms Head-on overlap of orbitals Sideways overlap of orbitals
covalent bond - the distance between the centers of the nuclei of two bonded atoms σ bonds - an increase in the electron density between two nuclei π bonds - Sideways overlap of orbital hybridization - the mixing of atomic orbitals to produce a set of equal number of hybrid orbitals bond dissociation energy - the amount of energy needed to break apart a covalent bond
Electrons are distributed around an element in free radicals electron pairs singlets
electron pairs
Based on the resonance structures of benzene (see Figure F07-4-5), we can predict that there are three short C-C bonds and three long C-C bonds in benzene. True False
false
In a covalent bond it is no longer a requirement that the electrons in the bonding pair have opposite spins, i.e., they do not have to obey the Pauli exclusion principle. True False
false
Resonance can only occur when the elements in the molecule keep the same formal charge. True False
false
T or F: Lithium bromide (LiBr) has a smaller lattice energy then sodium bromide (NaBr).
false
The resonance structures of thiocyanate ion, SCN− depicted in Figure F07-4-4 are equivalent. True False
false
Match these words with their definition. formula weight molecular weight atomic weight - average molecular mass of the collection of atoms represented by the chemical formula for a molecule - The mass of a formula unit. - the average mass of the atoms of an element
formula weight - the mass of a formula unit. molecular weight - average molecular mass of the collection of atoms represented by the chemical formula for a molecule atomic weight - the average mass of the atoms of an element
What electron domain geometry will be associated with a molecule that has a steric number of 2? octahedral tetrahedral trigonal planar trigonal bipyramidal linear
linear
What is the canonical shape associated with a molecule that has 6 bonded atoms and no lone pairs? trigonal bipyramidal tetrahedral trigonal planar linear octahedral
octahedral
What is the molecular geometry of SF6? octahedral linear trigonal bipyramidal tetrahedral trigonal planar
octahedral
What is the molecular geometry associated with a molecule that has 4 bonded atoms and 1 lone pair (AX4E1). (See Table T08-2-1 if you need help with this.) seesaw T-shaped linear bent trigonal bipyramid
seesaw
What is the expected bond angle indicated in the molecule below (Between H and H)? H | H--N .. slightly > 109.5° slightly > 90° slightly < 90° 90° slightly < 109.5° 120° 109.5°
slightly < 109.5°
What type of hybrid orbitals form when 2 atomic orbitals are mixed? sp sp2 sp3
sp
If a molecule has bond angles of 120° between the atoms, what type of hybrid orbitals are on the central atom in the molecule? sp sp2 sp3
sp2
If a molecule has trigonal planar electron domain geometry, what type of hybrid orbitals are on the central atom in the molecule? sp sp2 sp3
sp2
What hybrid orbitals are used by boron for bonding in BF3? sp sp2 sp3
sp2
What type of hybrid orbitals form when 3 atomic orbitals are mixed? sp sp2 sp3
sp2
What hybrid orbitals are used by nitrogen for bonding in NF3? sp sp2 sp3
sp3
The number of electron domains found around the central atom is known as the... steric number valence number bond number atomic number electron number
steric number
What electron domain geometry will be associated with a molecule that has a steric number of 3? tetrahedral trigonal planar trigonal bipyramidal linear octahedral
trigonal planar
What is the molecular geometry about the central atom in the angle shown in the molecule below? O || C --C-- O trigonal planar tetrahedral bent trigonal bipyramid trigonal pyramid
trigonal planar
A covalent bond is an increase in electron density between nuclei caused by orbital overlap. True False
true
Some molecules cannot be accurately represented by a single Lewis structure. True False
true
T or F: Calcium oxide (CaO) has a larger lattice energy then potassium chloride (KCl).
true
T or F: In valence bond theory, covalent bonds are described in terms of the overlap of atomic or hybrid orbitals.
true
T or F: Polarity of a molecule is determined by bond polarity and molecular geometry.
true
In the formula below, what is NLS? FC = NV − NLS the number of valence electrons in the Lewis structure of the molecule or ion the number of valence electrons on one atom in the Lewis structure ½ of the bonded electron pairs in the Lewis structure ½ of the non bonded electron pairs in the Lewis structure ½ of the bonded electron pairs and all of the lone pairs in the Lewis structure. ½ of the bonded electron pairs and all of the lone pairs on one atom in the Lewis structure.
½ of the bonded electron pairs and all of the lone pairs on one atom in the Lewis structure
