chem for engineers Exam 3 study questions
Consider the combustion of ethane, C2H6 C2H6(g) + O2(g) ARROW CO2(g) + H2O(l) Given Change in Gf in KJ/mol: C2H6= -32.9, O2= 0, CO2= -394.4, and H2O= -237.2. What is the change in G? a.) -2935.0 KJ b.) 2935.0 KJ c.) -598.7 KJ d.) -2277.8 KJ
A
Doping pure silicon with arsenic results in a(n) ______ material. a.) n-type b.) d-type c.) s-type d.) p-type
A
How many double bonds are in N2H2? a.) 0 b.) 1 c.) 2 d.) 3
A
If energy is used to move a mass over a distance against resistance, the _________ has been performed: a.) Work b.) Acceleration c.) Heat d.) Joule
A
If the orbitals of two atoms overlap and interact with constructive interference, the resulting increase in wave density results in a(n): a.) Bonding molecular orbital b.) Anti-bonding molecular orbital c.) Cation formation d.) Free radical formation
A
The entropy of a system approaches zero as: a.) The system approaches absolute zero b.) The system surpasses the boiling point of its highest boiling component c.) It reacts with a halogen gas
A
Two 6.5 L flasks are joined by a 150 ml tube with a stop cock. If 0.25 moles of nitrogen are held in the left flask and the right flask is empty, what happens to the entropy of the system upon opening the valve between the flasks? a.) The entropy increases b.) The entropy remains the same c.) There is too little information to be able to determine the change d.) The entropy decreases
A
Two different metals of equal mass with different heat capacities are separately subjected to the same amount of heat. Which one undergoes the smaller change in temperature? a.) The metal with the larger heat capacity b.) You need to know the initial temperature of the metals c.) The metal with the smaller heat capacity d.) Both undergo the same change in temperature
A
Which bond will be longer then C - O? a.) C - S b.) C = O c.) O - O d.) O = O e.) all the same length
A
Which pair of atoms is most likely to be involved in hydrogen bonding? a.) H and O b.) Na and H c.) H and Cl d.) Fe and H
A
Which of the following will act on CH3OCH3? a.) Dispersion forces b.) Dipole- induced dipole c.) Ion- dipole d.) Ion-ion e.) Dipole- Dipole f.) Ion- induced dipole g.) Hydrogen bonding
A & E
Trigonal Planar- Linear
AX2
Trigonal Planar- Bent
AX2E
Tetrahedral- Bent
AX2E3
Trigonal Bypyramida- Linear
AX2E3
Octahedral- Linear
AX2E4
Trigonal Planar- Trigonal Planar
AX3
Tetrahedral- Trigonal Pyramidal
AX3E
Trigonal Bypyramida- TShaped
AX3E2
Octahedral- TShaped
AX3E4
Tetrahedral- Tetrahedral
AX4
Trigonal Bypyramida- Seesaw
AX4E
Octahedral- Square Planar
AX4E2
Trigonal Bypyramidal- Trigonal Bypyramidal
AX5
Octahedral- Square Pyramidal
AX5E
Octahedral- Octahedral
AX6
?? If a 136.5 g aluminum rod (c= 0.900 J/g Celcius) at 100.0 degrees celcius is placed onto 250.0 g of water (c for water = 4.18 J/g Celcius) at 21.8 degrees celcius, what is the temperature of the system (rod and water) at equillebrium, assuming no heat lost to the surroudings? a.) 206 C b.) 30 C c.) 18 C d.) 46 C
B
?? What amount of heat is required to warm 293.4 g of water ice at -11.0 Celcius to steam at 153.3 Celcius? Assume the specific heat of water to be 4.18 J/g Celcius, Change in H(fusion) = 3.35 J/g, Change in H(vap) = 2.26 KJ/g. a.) 63.7 KJ b.) 865 KJ c.) 743 KJ d.) 110 KJ
B
Consider the best Lewis structure for N2O. Which of the following statements is correct? a.) Molecule is a radical b.) Formal charge on oxygen is -1 c.) There is a nitrogen- nitrogen double bond d.) Oxygen is the central atom e.) Molecule involves an atom with an expanded octete
B
Consider the reaction of carbon monoxide with oxygen to produce carbon dioxide: 2 CO + O2 ARROW 2 CO2 At which temperature will this reaction become spontaneous according to Gibbs energy? changeHf for CO= -110.5, O2= 0, CO2= -393.5; S for CO= 197.6, O2= 205.0, CO2= 213.6 a.) Above -63.1 K b.) Above 3272 K c.) Above 179.5 K d.) Above 415.8 K
B
Sodium chloride is an example of a(n) a.) amorphous solid b.) crystalline solid c.) covalent network d.) metallic solid
B
The second law of Thermodynamics states that: a.) Fires can never burn to completion b.) It is impossible to convert completely an engine's heat to work c.) Every action has an equal and opposite reaction d.) Force is equal to mass multiplied by acceleration
B
Which of the following substances has the lowest boiling point? a.) HF b.) Ar c.) C2H6 d.) CH2Cl2
B
A chemical reaction in which the bonds formed are stronger (have more energy) than those broken is referred to as a(n): a.) Inverse Reaction b.) Exothermic Reaction c.) Endothermic Reaction d.) Systematic Reaction
C
At what temperature is the Entropy of a water sample the lowest? a.) 99 C b.) 135 C c.) -15 C d.) 2 C
C
Identify the best set of bonds for the Cyanate: NCO- and fulminate: CNO- ions. (=- means 3 bonds) a.) (N =-C-O)- & (C=N=O) b.) (N=C=O) & (C=N=O) c.) (N=-C-O) & (C=-N-O) d.) (N=-C-O) & (C-N=-O)
C
The phase transition between liquid and solid phases is known as the: a.) Condensation b.) Sublimation c.) Fusion d.) Vaporization
C
Under constant volume conditions, the change in internal energy equals the: a.) Transduction b.) Entropy c.) Heat Flow d.) Insulation Capacity
C
What are the primary products in the combustion of a hydrocarbon? a.) H2 and O2 b.) C and H2 c.) H2O and CO2 d.) CO and H2O
C
What term is used to most accurately describe the energy flow from a warm object to a cooler object? a.) Cascade b.) Work c.) Heat d.) Acceleration
C
Which of these changes will always result in an increase in the internal energy of the system? a.) System absorbs heat and does work on the surroundings b.) system releases heat an does work on surrounding c.) system absorbs heat and has work done on it by the surroundings d.) system releases heat and has work done by its surroundings
C
Which of these materials is an example of an ionic crystalline solid? a.) SiC b.) C60 c.) SrCl2 d.) C
C
Band gaps tend to be smallest for: a.) modulators b.) semiconductors c.) insulators d.) conductors
D
Calculate the change in S for the reaction: 2NO2 ARROW N2 + 2 O2 S: NO2= 240.0, N2= 191.5, O2= 205.0 a.) -480 KJ b.) 157 KJ c.) -157 KJ d.) 121.5 KJ
D
Consider the formation SF6. Using VESPR, which molecular shape best describes the shape of the molecule? a.) Square Planar b.) Tetrahedral c.) Square Pyramidal d.) Octahedral
D
How many "equivalent" atoms belong to a single simple cube unit cell? a.) 4 b.) 2 c.) 3 d.) 1
D
If a lighter contains 4.0 ml of liquid butane, C4H10 (density= 0.8g/ml)- how much potential energy does the lighter contain according to the combustion of butane: 2 C4H10 + 13 O2 ARROW 8 CO2 + 10 H2O Change in H = -5.75 X 10^3 KJ a.) 4.8 X 10^3 KJ b.) -8.0 X 10^2 KJ c.) -3.2 X 10^2 KJ d.) -1.6 X 10^2 KJ
D
Most Polar? a.) C - N b.) O - N c.) N - Cl d.) C - Cl
D
Predict the molecular shape/ geometry and bond of Sulfur sichloride SCl2: a.) Linear, 180 degrees b.) Trigonal Planar, 120 degrees c.) Trigonal Pyramidal, <109.5 degrees d.) Bent (V-shaped), <109.5 degrees
D
Strongest inter-molecular forces of attraction: a.) CH3COCH2CH2CH3 b.) CH3CH2CH2CH2CH2OH c.) CH3CH2CH2CH2CH2CH3 d.) HOH2C-CH=CH-CH2OH
D
The ability to bend a metallic solid is described by the metals: a.) ductility b.) polymeric break point c.) mobility d.) malleability
D
What is the exception to the Octet rule? a.) NF3 b.) H3O+ c.) PCl3 d.) IF4+
D
Which of the following reactions corresponds to the standard enthalpy of formation of NaF(s)? a.) 2 Na(s) + F2(g) ARROW 2 NaF(s) b.) Na(s) + .5 F2(s) ARROW NaF(s) c.) Na(s) + F(g) ARROW NaF(s) d.) Na(g) +.5 F2(g) ARROW NaF(s)
D
Which of these substances involves no intermolecuar bonding forces except for London dispersion forces? a.) H2O b.) HCl c.) HF d.) N2
D
Which phase change is exothermic? a.) Melting b.) Evaporation c.) Sublimation d.) Condensation
D
Which pure substances will not form hydrogen bonds? I.) CH3CH2OH II.) CH3OCH3 III.) H3C-NH-CH3 IV.) CH3F a.) I & II b.) I & III c.) II & III d.) II & IV
D
What is a pi bond?
Double bonds
T/F All reactions with a positive delta(S) are spontaneous regardless of temperature.
False
T/F All spontaneous processes occur very rapidly.
False
T/F An electron accelerated to velocity of 3.81 x 10^3 m/s will have more energy than a proton accelerated to the same velocity.
False
What is a sigma bond?
The number of bonds there is (double and triple bonds equals 1 when counting)
T/F A substance that solidifies into a random arrangement is referred to as an amorphous solid.
True
T/F As the velocity of moving object doubles, the kinetic energy of the object quadruples.
True
T/F Entropy is a state function.
True
T/F The most favored arrangement of four atoms around a central atom is referred to as a tetrahedral shape.
True
T/F The valence shell electron pair repulsion (VESPR) theory states that molecules assume a shape that minimizes the repulsion between electron pairs and bonded atoms in the valence shell of the central atom.
True
T/F Thermal energy is directly related to the motion of atoms and molecules of the object in question.
True
T/F Thermochemistry describes the energetic consequences of a chemical reaction.
True
How do you determine the more polar atom?
largest diff in electronegativity or top right
