101 CHEM SAMPLE EXAM (FINAL): The answers are on a separate document. If I were you, i'll answer first before looking at the answers.
(1) Which formula/name combination(s) is (are) incorrect? 1) Be3N2 / berium nitride 2) (NH4)2S / ammonium sulfide 3) CuCO3 / copper(II) carbonate 4) SF4 / sulfur(IV) fluoride 3&4 2&3 1&3 1,2&4 1&4 (2)The following reaction is important in the recovery of gold from ores: a Au + b KCN + c O2 + d H2O --> e KAu(CN)2 + f KOH
The sum, (a+b+c+d+e+f), of the smallest integer coefficients in the balanced equation is 23 12 16 8 18 (3) Naturally occurring Mg has three isotopes: Mg-24 (23.99 amu), Mg-25 (24.99 amu) and Mg-26 (25.98 amu). The natural abundance of Mg-24 is 79.00%. What is the abundance (%) of Mg-25 ? 10.50 11.01 10.00 21.00 not enough information given to answer. (4) Main-group 8 elements have which of the following properties? 1) They are gases at room temperature and 1 atm pressure 2) They are easily ionized and thus conduct electricity in the liquid state 3) They are very stable substances and react with few other elements 4) They are shiny, low melting, solids and are good conductors of heat and electricity 3&4 1&3 1,2 &3 2&4 2 (5) The compound ferrocene is 64.46% carbon by mass. If there are ten carbon atoms in one ferrocene molecule, what is the molecular mass (amu) of ferrocene?
774.7 120.1 645.6 186.3 7754 (6) 50.0 mL of 0.10M AgNO3 (aq) is added to 25.0 mL of 0.050M NaCl(aq). The reaction AgNO3(aq) + NaCl(aq) --> AgCl(s) + NaNO3(aq) occurs. What is the molar concentration of Ag+(aq) in the solution? 0.025 0.125 0.0 0.0375 0.050 (7)Given: ZrC(s) + 4Cl2(g) --> ZrCl4(g) + CCl4(g) ZrCl4(g) + 2 Mg(s) --> Zr(s) + 2 MgCl2(s) How many grams of Cl2(g) are required to produce 175g of Zr(s)? 544 136 700 103 364 (8) A type of sandstone consists of silica, SiO2, and calcite, CaCO3. When the sandstone is heated, CaCO3 decomposes to CaO(s) and CO2(g). If 21.8 g of sandstone produces 4.29 L of CO2(g) at 1.0 atm and 573 K, what is the mass-percent of silica in the rock? 17.2 41.8 19.3 58.3 25.1 (9)How many liters of NH3(g), measured at 273 K and 1.0 atm, are required to prepare 25.0 mL of 2.50M NH3(aq)? 56 0.063 1.40 0.56 1400 (10) Which of the following statements is (are) true? 1) PV=nRT is a good approximation for real gases, especially at high pressure and low temperature. 2) An ideal gas is made up of molecules or atoms with no intermolecular attractions and with negligible volume. 3) At very high pressure, the deviation of a real gas from ideality is due primarily to finite molecular or atomic volume. 4) For the noble gases, the value of the Van der Waals b parameter increases in the order Ne < Ar < Kr < Xe.
3 2,3&4 1&4 2&3 1,2&3 (11) 1.35 atm of PCl5(g) is introduced into an evacuated 1.00 L container. After one hour, 24.0% of the PCl5 has decomposed to PCl3(g) and Cl2(g), the temperature remaining constant. What is the total pressure (atm) in the container? 1.03 2.00 1.35 1.67 0.648 (12) Given: 2 CH3OH(l) + 3 O2(g) --> 2 CO2(g) + 4 H2O(g)
StandardDeltaH(formation) [kJ/mol]: CH3OH = -238.7; CO2 = -393.5; What is StandardDeltaH(rxn) [kJ] 132 -291 -213 -638 -426
H2O = -241.8
if 1.00 mol of O2 is reacted with excess CH3OH?
(13) Given: Bond energy (kJ/mol): Cl-Cl = 243, Br-Br = 193, Br-Cl = 218. Evaluate H(rxn) [kJ] for Br2(g) + Cl2(g) --> 2 BrCl(g). 0 -218 -872 218 872 (14) Given: Bond energy (kJ/mol): H-H = 435, O=O = 498; StandardDeltaH(formation) [kJ/mol]: H2O(g) = -241.8 Evaluate StandardDeltaH(rxn) [kJ] for H2O(g) --> 2 H(g) + O(g). 242 -442 926 442 1175 (15) The successive ionization energies (MJ/mol) of an element are: 0.58, 1.82, 2.74, 11.58, 14.83, 18.38,... The element is most likely @ Mg B Si Al
S (16) For n=3, how many sets of four quantum numbers are possible? 3 18 9 16 8 (17) Using ultraviolet spectroscopy, astrophysicists determined that 7.8E28 water molecules were being evaporated per second from Halley's comet while it was still 310E6 km from the sun. How many metric tons (1 metric ton = 1000 kg = 2200 pounds) of water does Halley's comet lose each second? 2.3 0.0067 0.12 1.3E24 4.0E27 (18) Which of the following are permitted EXCITED STATES for Al? 3s 3p 1) [Ne] - - ----- ---2) [Ne] 3) [Ne] 4) [Ne] 2,3&4 3 4 1 none of them (19) An element has the electron configuration [Ne],3s2,3p4. Which of the following statements is (are) true? 1) the element exists as a shiny solid at room conditions 2) the element can form compounds with expanded octets 3) the element is often reacted with H2 to produce ammonia by the Haber process 4) the element can be reacted with oxygen to produce a gas which is an acid anhydride. 1 3&4 3 2&3 2&4 (20) What is the most likely product of the reaction between aluminum and sulfur? Al3S ------- -- ----- ----- -----
- --
AlS3 Al2S3 Al(III)S Al3S2 (21) Which is the ground state electron configuration of Fe(2+)? 3d 4s [Ar] - - - -- - -- - -- - -- [Ar] - -- -- -- -- -- -- -- -- -- -- -- -- -------- -----
[Ar] - -[Ar] -
[Ar] - --
- --
(22) Which is the preferred Lewis structure for OCS? *the lines on top of atoms are lone pairs...between atoms, they are bonds :O-CS: :OC-S: - - :O-C-S: - - :O-C-S: - - :O=C=S: (23) Which of the following are polar molecules (have a net dipole moment)? 1) PF5 2) SeCl4 3)SiF2 4) FCCF all of them 2,3&4 1,2&3 1&3 2&3 (24) Which is the correct order of decreasing bond polarity? Cs-F Li-I Cs-F Li-I > > > > Li-I > O-F > N-F N-F > O-F > Cs-F Li-I > N-F > O-F Cs-F > N-F > O-F
O-F > N-F > Li-I > Cs-F (25) For NO3-, which of the following statements is (are) true? 1) Each NO bond is longer than an ordinary NO single bond and shorter than an ordinary NO double bond 2) Each NO bond is shorter than an ordinary NO single bond and longer than an ordinary NO double bond 3) Each NO bond is the same length 4) Since NO3- consists of three resonance forms, the shape of the ion is trigonal bipyramidal. 1 4 1,2&3 1,2&4 2&3 [:N-CO:]- one represents of the resonance structures of the cyanate ion. The formal charge on the N,C, and O atoms, respectively, is (26) The Lewis formula +2,0,-1 -2,0,+1 -2,+4,-1 0,0,-1 -2,0,-1 (27) The orbitals used by N in NH3 are called (--1--) hybrids. The molecule has a (--2--) shape and will (--3--) polar. The blanks are filled in as follows: (--1--) (--2--) (--3--) sp2 sp2 sp3 sp3 sp2 trigonal pyramidal trigonal planar trigonal planar trigonal pyramidal tetrahedral be not be not be be be C // \ H-CC-C H-C H O // C-C O C-C \\ O
(28) In the molecule whose Lewis structure is shown to the right, the number of carbon atoms with designated hybridization is
sp3 1 2 1 2 2
sp2 7 6 6 7 6
sp 2 3 3 2 2
\ // H C CN:
(29) In which of the following molecules and ions does the central atom use sp3 hybrid orbitals? 1) CH4 2) OF2 3) SF4 4) H3O+ 1 1&3 1&4 1,2&4 all of them (30) The triatomic molecule XY2 is nonpolar and each Y atom is bonded to the central X atom by a sigma and a pi bond. What orbitals are used by the X atom? 1) sp 2) s 3) sp2 4) sp3 5) p 1&2 3&5 1&5 4 4&5 (31) In the molecule FCCCH3, there are (--1--) lone-pair electrons, (--2--) electrons in sigma bonds, and (--3--) electrons in pi bonds. blanks are filled in as (--1--) (--2--) (--3--) 0 6 6 6 6 4 10 4 6 12 6 6 6 4 4 C1 - C2 - C3 ,
(32) In the molecule shown below, what are the angles C2 - C3 - C4 , and C4 - C5 - C6 respectively? H H H H H-C1-C2-C3=C4-C5C6-H H H 120, 180, 90 180, 90, 120 109, 120, 180 90, 109, 120 109, 180, 180 C(2) has 4 single bonds and is thus C-C(2)-C angle is 109. C(3) has 2 bonds and is thus sp2 hybridized so C(5) has 1 single bond and 1 triple so the C-C(5)-C bond angle is 180.
sp3 hybridized so the single bonds and 1 double the C-C(3)-C angle is 120. bond and is thus sp hybridized
(33) When 30.0 mL of 0.100 M Ba(OH)2 solution is mixed with 45.0 mL of 0.152 M HCl solution, a solution with a total volume of 75 mL is formed. What is the concentration of the excess hydrogen
or hydroxide ions in the final solution? 0.028 M H+(aq) 0.011 M H+(aq) 0.019 M OH-(aq) 0.051 M H+(aq) 0.085 M OH-(aq) (34) A 5.00 L flask initially containing He at 5.00 atm is connected to a 4.00 L flask initially containing N2 at 4.00 atm to form a single 9.00 L container for both gases. What are the partial pressures (in atm) of He and N2, respectively, in the 9.00 L container? 5.00, 4.00 0.555, 0.444 2.78, 1.78 9.00, 9.00 1.00, 1.00 (35) In a coffee cup calorimeter of negligible heat capacity, 50. mL of 0.20 M Ba(OH)2 and 50. mL of 0.40 M HCl are mixed. The heat of neutralization, H(neut.) = -56.9 kJ/mol for H+(aq) + OH-(aq) --> H2O(l) What is the temperature change (in Kelvin) in the calorimeter? The solution has a specific heat capacity of 4.184 J/K-g and a density of 1.00 g/cm^3. +2.7 +5.4 -2.7 -5.4 +1.4 K K K K K
(36) The diffusion rate of an unknown gas is 43.07 mL/min. Under identical conditions, the diffusion rate of O2 is 30.50 mL/min. What is the identity of the unknown gas? NO2 CO NO CO2 CH4 (37) If there are 3.00 mol of N2(g) and 4.00 mol of O2(g) in a sealed container at a total pressure of 2.00 atm, which statement is CORRECT about their partial pressures, P(N2) and P(O2) ? P(N2) and P(O2) cannot be knowledge of the absolute P(N2) = 6.00 atm, P(O2) = P(N2) = 0.86 atm, P(O2) = P(N2) and P(O2) cannot be knowledge of the volume P(N2) = 1.00 atm, P(O2) = determined without a temperature 8.00 atm 1.14 atm determined without a 1.00 atm
(38) According to Avogadro's Hypothesis, if at STP 4.0 L of N2(g) and 4.0L of O2(g) are allowed to react to form N2O4(g),
which of the following statements is INCORRECT about the mixture before the reaction begins? -There are equal numbers of N2 and O2 molecules present in the reaction mixture. -There are 0.18 moles of N2 in the reaction mixture. -There are 1.1 E23 molecules of O2 in the reaction mixture. -There is excess N2 in the reaction mixture. -There is excess O2 in the reaction mixture. (39) What is the oxidation number of N in Cd(NO3)2 ? +5 +6 +4 -1 -5 (40) Which ion below has the largest radius? Mg(2+) Te(2-) O(2-) Sr(2+) Ba(2+) (41) When 10.00 g 270C, a reaction residue is 9.20 g empirical formula CrO Cr2O3 CrO2 Cr2O5 Cr (42) Which one of the following is a strong electrolyte? CO2 XeF3 HCl ClF3 Cl2 (43) Estimate the enthalpy change for the reaction below given the following bond energies: BE(S-O) = +347 kJ; BE(O=O) = +499 kJ 2 SO3(g) -195 +195 -152 +152 +846 kJ kJ kJ kJ kJ _?_ bonding pair(s) and _?_ lone --> O2(g) + 2 SO2(g) of solid red chromium(VI) oxide, CrO3 is heated at occurs, during which O2(g) is given off. The of a powdered brown compound. What is the of the brown compound?
(44) The central Br atom in BrF5 has
(unshared) pair(s) of electrons? 5, 1, 6, 3, 5, 0 5 0 3 1
(45) What type of hybrid orbitals are used by the central atom in SF4? 3 2 sp d 3 sp d 3 sp 4 spd 2 3 sp d (46) The first step in the commercial synthesis of nitric acid is shown in the balanced equation below. If a reaction vessel contains 10.0 atm of NH3(g) and 11.5 atm of O2(g) at the constant temperature of 400K, what will be the partial pressure of the NO produced in the reaction? 4 NH3(g) 10.0 11.5 21.5 9.2 need + 5 O2(g) --> 4 NO(g) + 6 H2O(g)
atm atm atm atm to know the volume of the vessel
(47) Which series of elements below would have most nearly the same atomic radius? O,F,Na,Mg F,Cl,Br,I He,Ne,Ar,Kr B,Si,As,Te V,Cr,Mn,Fe (48) Given a gas sample containing n moles of gas at Kelvin temperature T, volume V, and pressure P. You now remove n/3 moles of gas from the container at constant T and V. What change occurs? the pressure the pressure the pressure the pressure more data is would change would change would change would change needed to to to to 3P/2 2P/3 3P P/3
(49) Which of the following molecules is polar? an octet of electrons. F \ B-F / F -S // \\ O O
All F's & O's have F F \ P-F / F F
(A)
(B)
(C)
A & B B & C A & C A,B & C B only (50) Which one of the following species is NOT planar? BF3 AlCl3 XeF4 PCl3 NO3(-)