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100 Practice Questions for Chem 1C Midterm 1 - Joseph
- Which of the following statements is incorrect? A) Ionic bonding results from the transfer of electrons from one atom to another. B) Dipole moments result from the unequal distribution of electrons in a molecule. C) The electrons in a polar bond are found nearer to the more electronegative element. D) A molecule with very polar bonds can be nonpolar. E) Linear molecules cannot have a net dipole moment.
- Which of the following shows these molecules in order from most polar to least polar? A) CH 4 > CF 2 Cl 2 > CF 2 H 2 > CCl 4 > CCl 2 H 2 B) CH 4 > CF 2 H 2 > CF 2 Cl 2 > CCl 4 > CCl 2 H 2 C) CF 2 Cl 2 > CF 2 H 2 > CCl 2 H 2 > CH 4 = CCl 4 D) CF 2 H 2 > CCl 2 H 2 > CF 2 Cl 2 > CH 4 = CCl 4 E) CF 2 Cl 2 > CF 2 H 2 > CCl 4 > CCl 2 H 2 > CH 4
- Which of the following is polar? A) SiF 4 B) XeF 2 C) BCl 3 D) NBr 3 E) SBr 6
- Which statement is correct? A) H 2 O is linear. B) The molecule ClO 2 cannot be accurately described by a Lewis structure consistent with the octet rule. C) The diatomic molecule Cl 2 is an example of a polar molecule. D) The bonds in LiF have a more covalent character than those in F 2. E) none of these
Use the following to answer question 5:
Consider the following molecules. I. BF 3 II. CHBr 3 (C is the central atom.) III. Br 2 IV. XeCl 2 V. CO VI. SF 4 Select the molecule(s) that fit the given statement.
- These molecules have a zero net dipole moment. A) III, V B) I, III, IV C) III, IV, V D) I, III, IV, VI E) none of them
- Select the best Lewis structure for acetone, CH 3 COCH 3.
A)
B)
C
H
H
H C O C H
H
H
C
H
H
C H
O
H C
H
H
C)
D)
E)
- The Lewis structure for H 3 BO 3 is A)
B)
C)
D)
E)
- Which of the following is not a valid resonance structure for N 3 –?
A)
B)
C)
D)
E) All are valid.
C
H
H
H
C O H C H
H
H H O
H
C C C H
H
H
C
H
H
H
C
H
H
C
H
O
H O O H
O
B
H
H O B
O
H
O H
H O B
O
H
O H
H O B
O
H
O H
H O B
O
H
O H
N N N
N N N
N N N
N N N
- How many of the following molecules and ions are linear? NCl 3 NH 4 +^ SCN-^ CO 2 NO 2 - A) 0 B) 1 C) 2 D) 3 E) 4
- What type of structure does the XeOF 2 molecule have? A) pyramidal B) tetrahedral C) T-shaped D) trigonal planar E) octahedral
- Which ion is planar? A) PF 4 + B) CO 32 – C) SO 32 – D) ClO 4 – E) SCl 5 -
- Select the correct molecular structure for PO 33 –. A) pyramidal B) tetrahedral C) square planar D) octahedral E) none of these
- Which of the following molecules contains a nitrogen atom that is sp^2 hybridized? A) NH 3 B) NO 3 - C) N 2 D) HCN E) C 2 N 2
- Consider the structure of glycine, the simplest amino acid:
What is the total number of bonds in the molecule? A) 0 B) 1/ C) 1 D) 2 E) More information is needed.
- What is the hybridization of I in the molecule ICl 3? A) sp B) sp^2 C) sp^3 D) dsp^3 E) d^2 sp^3
H 2 N C C OH
H O
H
- What is the hybridization of S in the molecule H 2 S? A) sp B) sp^2 C) sp^3 D) dsp^3 E) d^2 sp^3
- What is the hybridization of C in the ion CN-? A) sp B) sp^2 C) sp^3 D) dsp^3 E) d^2 sp^3
- Atoms that are sp^3 hybridized form ____ pi bond(s). A) 0 B) 1 C) 2 D) 3 E) 4
- What is the hybridization of the central atom in SF 6? A) sp B) sp^2 C) sp^3 D) dsp^3 E) d^2 sp^3
- What is the hybridization of the central atom in IF 5? A) sp B) sp^2 C) sp^3 D) dsp^3 E) d^2 sp^3
- What is the hybridization of the central atom in SF 4? A) sp B) sp^2 C) sp^3 D) dsp^3 E) d^2 sp^3
- Consider the following molecule. (Lone pairs are not drawn in.)
Specify the hybridization of each carbon atom (in numeric order: C-1 C-2 C-3 C-4 C-5). A) sp^2 sp^2 sp^2 sp^3 sp B) sp^2 sp^2 sp^2 sp^3 sp^3 C) sp^2 sp^2 sp^3 sp^3 sp D) sp^2 ssp^2 sp^3 sp^3 sp^3 E) sp sp sp sp^2 sp
H 2 C CH C CH 2 C N
O
1 2 3 4 5
Use the following to answer questions 34-36:
Tetracyanoethylene has the skeleton shown here:
From its Lewis structure, determine the following.
- How many sigma bonds and how many pi bonds are in the molecule? A) 5 sigma and 9 pi B) 6 sigma and 8 pi C) 9 sigma and 7 pi D) 9 sigma and 9 pi E) 5 sigma and 8 pi
- How many of the atoms are sp^2 hybridized? A) 2 B) 4 C) 6 D) 8 E) 10
- How many of the atoms are sp hybridized? A) 2 B) 4 C) 6 D) 8 E) 10
- Which of the following has the shortest N-O bond? A) NO 3 – B) NO+ C) N 2 D) NO 2 – E) none of these
- Complete the Lewis structure for the following molecule.
This molecule has __________ sigma bonds and __________ pi bonds. A) 4, 5 B) 6, 3 C) 11, 5 D) 13, 2 E) 13, 3
CH
CH 3
CH 3 C
O
C N
- Which of the following statements is correct? A) A triple bond is composed of two bonds and one bond. B) bonds result from the head-to-head overlap of atomic orbitals. C) Free rotation may occur about a double bond. D) bonds have electron density on the internuclear axis. E) More than one of these statements are correct.
- As the bond order of a bond increases, its bond energy ______ and its bond length ______. A) increases, increases B) decreases, decreases C) increases, decreases D) decreases, increases
- If four orbitals on one atom overlap four orbitals on a second atom, how many molecular orbitals will form? A) 1 B) 4 C) 8 D) 16 E) none of these
- For which of the following diatomic molecules would the bond order become greater if an electron were removed, that is, if the molecule were converted to the positive ion in its ground state? A) B 2 B) C 2 C) P 2 D) F 2 E) Na 2
- Which of the following species has the largest dissociation energy? A) O 2 B) O 2 – C) O 22 – D) O 2 + E) O 2 2+
- Which of the following is paramagnetic? A) B 2 B) C 2 C) H 2 D) N 2 E) F 2
- Order the following from shortest to longest bond: C 2 , B 2 , H 2 , N 2 A) H 2 , N 2 , C 2 , B 2 B) N 2 , C 2 , B 2 , H 2 C) C 2 , N 2 , H 2 , B 2 D) C 2 , B 2 , H 2 , N 2 E) none of these
- Which of the following statements is true? A) Electrons are never found in an antibonding MO. B) All antibonding MOs are higher in energy than the atomic orbitals of which they are composed. C) Antibonding MOs have electron density mainly outside the space between the two nuclei. D) None of these statements is true. E) Two of these statements are true.
- Which of the following compounds has the lowest boiling point? A) CH 4 B) C 2 H 6 C) C 3 H 8 D) C 4 H 10 E) C 5 H 12
- Which of the following compounds has the highest boiling point? A) C 2 H 6 B) CO C) H 2 D) N 2 E) Ne
- Which of the following compounds has the highest boiling point? A) CH 4 B) H 2 O C) NF 3 D) O 2 E) He
- Which substance involves no intermolecular forces except London dispersion forces? A) K B) H 2 S C) NaF D) H 2 E) HCl
- The elements of Group 5A, the nitrogen family, form compounds with hydrogen that have the boiling points listed below. SbH 3 – 17°C, AsH 3 – 55°C, PH 3 – 87°C, NH 3 – 33°C The first three elements illustrate a trend where the boiling point decreases as the mass decreases; however, ammonia (NH 3 ) does not follow the trend because of A) dipole-dipole attraction. B) metallic bonding. C) hydrogen bonding. D) London dispersion forces. E) ionic bonding.
- The resistance of a liquid to an increase in its surface area is called A) capillary action. B) surface tension. C) vapor pressure D) viscosity. E) none of these
- On the basis of your knowledge of bonding in liquids and solids, which of the following substances has the highest melting temperature? A) NaBr B) Br 2 C) NO 2 D) CF 4 E) H 2 O
- Which of the following is the correct order of boiling points for NaNO 3 , CH 3 OH, C 2 H 6 , and Ne? A) Ne < CH 3 OH < C 2 H 6 < NaNO 3 B) NaNO 3 < CH 3 OH < C 2 H 6 < Ne C) Ne < C 2 H 6 < NaNO 3 < CH 3 OH D) Ne < C 2 H 6 < CH 3 OH < NaNO 3 E) C 2 H 6 < Ne < CH 3 OH < NaNO 3
- In cubic closest-packed solids, what percentage of space is occupied by the spheres? A) 43.8% B) 52.4% C) 68.0% D) 74.0% E) none of these
- Which of the following is the smallest hole in a closest-packed lattice of spheres? A) trigonal B) tetrahedral C) cubic D) octahedral E) none of these
- Which substance can be described as cations bonded together by mobile electrons? A) Ag( s ) B) S 8 ( s ) C) Kr( l ) D) KCl( s ) E) HCl( l )
- What is the net number of face-centered atoms contained in a face-centered cubic unit cell? A) 1 B) 3 C) 4 D) 6 E) none of these
Use the following to answer questions 67-69:
The molar volume of a certain form of solid lead is 18 cm^3 /mol. Assuming cubic closest-packed structure, determine the following.
- The number of Pb atoms per unit cell A) 3 B) 4 C) 10 D) 12 E) 14
- The volume of a single cell A) 1.20 102 pm^3 B) 1.20 104 pm^3 C) 1.20 106 pm^3 D) 1.20 108 pm^3 E) none of these
- Chromium metal crystallizes as a body-centered cubic lattice. If the atomic radius of Cr is 1.25 angstroms, what is the density of Cr metal in grams per cubic centimeter? A) 5.52 g/cm^3 B) 7.18 g/cm^3 C) 7.81 g/cm^3 D) 2.76 g/cm^3 E) 3.59 g/cm^3
- You are given a small bar of an unknown metal, X. You find the density of the metal to be 10.5 g/cm^3. An X- ray diffraction experiment measures the edge of the unit cell as 409 pm. Assuming that the metal crystallizes in a face-centered cubic lattice, what is X most likely to be? A) Ag B) Rh C) Pt D) Pb E) none of these
- A certain solid substance that is very hard, has a high melting point, and is nonconducting unless melted is most likely to be A) I 2 B) KCl C) NO 2 D) H 2 O E) Cr
- The unit cell in a certain lattice consists of a cube formed by an anion at each corner, an anion in the center, and a cation at the center of each face. The unit cell contains a net A) 5 anions and 6 cations. B) 5 anions and 3 cations. C) 2 anions and 3 cations. D) 3 anions and 4 cations. E) 2 anions and 2 cations.
- A certain metal fluoride crystallizes in such a way that the fluoride ions occupy simple cubic lattice sites, while the metal atoms occupy the body centers of half the cubes. What is the formula for the metal fluoride? A) MF 2 B) M 2 F C) MF D) MF 8 E) none of these
- Sodium oxide (Na 2 O) crystallizes in a structure in which the O^2 –^ ions are in a face-centered cubic lattice and the Na+^ ions are in tetrahedral holes. What is the number of Na+^ ions in the unit cell? A) 2 B) 4 C) 6 D) 8 E) none of these
- In the unit cell of sphalerite, Zn2+^ ions occupy half the tetrahedral holes in a face-centered cubic lattice of S^2 – ions. What is the number of formula units of ZnS in the unit cell? A) 5 B) 4 C) 3 D) 2 E) 1
- A p -type semiconductor A) is made by doping host atoms with atoms having more valence electrons than the host. B) is made by doping host atoms with atoms having fewer valence electrons than the host. C) has electrons that lie close in energy to the conduction bands. D) two of these E) none of these
- Which of the compounds below is an example of a network solid? A) S 8 ( s ) B) SiO 2 ( s ) C) MgO( s ) D) NaCl( s ) E) C 25 H 52 ( s )
- Which of the following statements is true about p -type silicon? A) It is produced by doping Si with P or As. B) Electrons are the mobile charge carriers. C) It does not conduct electricity as well as pure Si. D) All are true. E) None is true.
- Doping Se with As would produce a(n) __________ semiconductor with __________ conductivity compared to pure Se. A) n -type, increased B) n -type, decreased C) p -type, increased D) p -type, decreased E) intrinsic, identical
- What is the vapor pressure of water at 100.0°C? A) 85 torr B) 760 torr C) 175 torr D) 1 torr E) More information is needed.
- Which of the following processes must exist in equilibrium with the condensation process when a measurement of vapor pressure is made? A) fusion B) evaporation C) sublimation D) boiling E) none of these
- Given below are the temperatures at which two different liquid compounds with the same empirical formula have a vapor pressure of 400 torr. Compound T (°C) dimethyl ether, CH 3 -O-CH 3 -37. ethanol, CH 3 CH 2 OH 63.
Which of the following statements is false? A) Increasing the temperature will increase the vapor pressure of both liquids. B) Intermolecular attractive forces are stronger in (liquid) ethanol than in (liquid) dimethyl ether. C) The normal boiling point of dimethyl ether will be higher than the normal boiling point of ethanol. D) The reason why the temperature at which the vapor pressure is 400 torr is higher for ethanol (than for dimethyl ether) is that there is strong hydrogen bonding in ethanol. E) None of these statements is false.
- Shown below is a phase diagram for compound X. At 25°C and 1 atm, in what state will X exist?
A) solid. B) liquid. C) gas. D) gas/liquid at equilibrium. E) gas/solid at equilibrium.
- A sample consisting of CO 2 ( g ) and CO 2 ( s ) at equilibrium at – 78°C and 1 atm pressure is heated to – 30°C, and the pressure is increased to 8 atm. Based on the phase diagram below, what will happen?
A) At equilibrium, only CO 2 ( g ) will be present. B) All the CO 2 will be converted to CO 2 ( l ). C) At equilibrium, CO 2 ( g ) and CO 2 ( l ) will be present. D) The melting point of the CO 2 ( s ) will decrease. E) none of these
- Shown below is a phase diagram for compound X. How will the melting point of X change with increased pressure?
A) It will increase. B) It will decrease. C) It will remain the same. D) There is not enough information given. E) It will increase and then decrease.
- Based on the phase diagram shown below, which of the following statements are correct?
I. Sublimation occurs at a point in the transformation that falls along a straight line from point A to point F. II. C and E represent points where the gas and liquid phases are in equilibrium.
III. H vap can be measured at point B. IV. Molecules at point D have a greater average kinetic energy than those at point F. V. The temperature at point E is called the critical temperature of the compound.
A) II, V
B) I, III, IV
C) I, II, III
D) II, IV, V
E) I, II, IV
- Choose the correct statement about the diagram below.
A) The diagram is qualitatively correct for water. B) The diagram shows that the melting point of the solid increases with increasing pressure. C) The diagram shows the triple point above 1 atm pressure. D) The diagram could represent the phase diagram of CO 2. E) None of these statements is correct.
- A certain substance, X, has a triple-point temperature of 20°C at a pressure of 2.0 atm. Which one of the following statements cannot possibly be true? A) X can exist as a liquid above 20°C. B) X can exist as a solid above 20°C. C) Liquid X can exist as a stable phase at 25°C, 1 atm. D) Both liquid and solid X have the same vapor pressure at 20°C. E) All of these statements could be true.
