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Question
Which substance has a standard enthalpy of formation equal to zero at 25ºC?A) C2H6(g)
B) Br2(g)
C) Br2(l)
D) Br2(s)
E) C2H6(l)
Answer
This answer is hidden. It contains 1 characters.
Related questions
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Which of the following molecules contains the ether functional group?
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B) CH3CH2OCH2CH3
C) CH3CH2OH
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E) H2O
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Which of the following statements is true about one formula unit of SrBr2?A) It is composed of one Sr atom and one Br2 molecule.B) It is composed of one Sr atom and two Br atoms.C) It is composed of one Sr2+ion and one Br22-ion.D) It is composed of one SrBr2molecule.E) It is composed of one Sr2+ion and two Br"ions.
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A sample of the mineral troegerite, (UO2)3(AsO4)2 - 12H2O, has 1.33 x 1021U atoms. How many arsenic atoms are present in this sample of troegerite?A) 2.00 x 1022B) 1.60 x 1022C) 2.66 x 1021D) 6.65 x 1022E) 8.87 x 1020
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All of the following elements are best classified as metalloids except
A) Si.
B) Te.
C) As.
D) B.
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Q:
Lithium has two naturally occurring isotopes, 6Li and 7Li . The average atomic mass of lithium is 6.941. Which of the following statements concerning the relative abundance of each isotope is correct?
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B) The abundance of 7Li is less than 6Li.
C) The abundance of 6Li is equal to the abundance of 7Li.
D) Not enough data is provided to determine the correct answer.
E) Based on the atomic mass, only 7Li occurs naturally.
Q:
Which of the following atomic symbols represents an isotope of ?
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Q:
Suppose atom 1 has the same number of protons as atom 2, and atom 2 has the same number of neutrons as atom 3. Atom 1 does not have the same number of neutrons as atom 3. Which of the following statements is true?
A) Atom 3 must have the same number of protons as atom 2.
B) Atoms 1 and 2 must be isotopes.
C) Atoms 1 and 3 must be isotopes.
D) Atom 2 must have the same number of neutrons as atom 1.
E) Atom 3 must have the same number of protons as atom 1.
Q:
The number of protons in a given nucleus determines the
A) mass number.
B) atomic number.
C) number of electrons.
D) number of protons.
E) number of isotopes.
Q:
If the Thomson model of the atom had been correct, Rutherford would have observed
A) alpha particles bouncing off the foil.
B) alpha particles going through the foil with little or no deflection.
C) alpha particles greatly deflected by the metal foil.
D) positive particles formed in the foil.
E) None of the above observations is consistent with the Thomson model of the atom.
Q:
A subatomic particle is
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B) only found in the nucleus of an atom.
C) always positively charged.
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E) always negatively charged.
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Cathode rays are
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Q:
For which of the following equilibria does Kc= Kp?
A) N2(g) + 3H2(g) 2NH3(g)
B) CO(g) + H2O(g) CO2(g) + H2(g)
C) CO(g) + 3H2(g) CH4(g) + H2O(g)
D) CaO(s) + CO2(g) CaCO3(s)
E) HBr(g) H2(g) + Br2(l)
Q:
For the reaction 2NO(g) + O2(g) 2NO2(g) at 750ºC, what is the relationship between Kc and Kp?A) Kc= KpB) Kc= Kp x (RT)-1C) Kc= Kp= 1.0D) Kc= Kp x (RT)E) Kc= Kp x (RT)1
Q:
The Ostwald process converts ammonia (NH3) to nitric oxide (NO) by reaction with oxygen in the presence of a catalyst at high temperatures. In a test of the process a reaction vessel is initially charged with 3.90 mol NH3(g) and 4.90 mol O2(g), sealed, and heated at a fixed high temperature. When equilibrium is established the reaction mixture is analyzed and found to contain 2.90 mol NO(g). What is the quantity of NH3(g) in the equilibrium reaction mixture?4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)A) 1.00 mol NH3(g)B) 6.80 mol NH3(g)C) 3.90 mol NH3(g)D) 1.28 mol NH3(g)E) 2.00 mol NH3(g)
Q:
Which of the following represents a dynamic equilibrium?
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B) a coin spinning in mid-air
C) two people of equal mass balanced on the ends of a seesaw
D) an open pan of boiling water
E) an object traveling at a constant speed
Q:
For the hypothetical reaction A → products, the concentration of A was monitored over time. From the following graph, what is the rate constant for the decomposition of A?A) -0.02735 s-1B) 2.3026 s-1C) -2.3026 s-1D) 0.02735 s-1E) 0.01188 s-1
Q:
Which of the following corresponds to the correct equation for the half-life of a first-order reaction?A) B) C) D) E)
Q:
The reaction A → products is first-order in A. If the concentration of A is cut in half, the half-life of the reaction willA) decrease by a factor of 1/2.B) double.C) decrease by a factor of 1/4.D) remain constant.E) quadruple.
Q:
A second-order reaction starts with an initial concentration of 0.100 mol/L of the reactant. If the rate constant is 3.6 x 10-2L/(mol·s), what is the time required to decrease the initial concentration to 0.050 mol/L?A) 280 sB) 420 sC) 19.3 sD) 1.39 sE) 830 s
Q:
A reaction that is second-order in one reactant has a rate constant of 2.2 x 10-2L/(mols). If the initial concentration of the reactant is 0.360 mol/L, how long will it take for the concentration to become 0.180 mol/L?A) 320 sB) 63 sC) 1300 sD) 32 sE) 130 s
Q:
The radioactive nuclide 63Ni decays by a first-order process via the emission of a beta particle. The 63Ni nuclide has a half-life of 100. years. How long will it take for 71% of 63Ni to decay?
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Q:
The nuclide 96Nb decays by a first-order process with a rate constant of 2.96 x 10-2 h-1. How long will it take for 82.0% of the initial amount of 96Nb to be consumed?A) 33.8 hB) 57.9 hC) 27.7 hD) 6.70 hE) 6.08 h
Q:
The reaction between selenous acid and the iodide ion in acid solution isH2SeO3(aq) + 6I-(aq) + 4H+(aq) → Se(s) + 2I3-(aq) + 3H2O(l)The data in the following table were measured at 0C. Experiment[H2SeO3]0(M)[H+]0(M)[I-]0(M)Initial Rate [mol/(L·s)]11.00 x 10-42.00 x 10-23.00 x 10-25.30 x 10-722.00 x 10-42.00 x 10-23.00 x 10-21.06 x 10-633.00 x 10-44.00 x 10-23.00 x 10-26.36 x 10-643.00 x 10-48.00 x 10-23.00 x 10-22.54 x 10-553.00 x 10-48.00 x 10-26.00 x 10-22.04 x 10-462.00 x 10-42.00 x 10-26.00 x 10-28.48 x 10-6Tripling the initial concentration of H2SeO3while holding the initial concentrations of H+ and I- constant increases the rate of the reaction by a factor ofA) 8.B) 4.C) 3.D) 2.E) 1.
Q:
The reaction between selenous acid and the iodide ion in acid solution isH2SeO3(aq) + 6I-(aq) + 4H+(aq) → Se(s) + 2I3-(aq) + 3H2O(l)The data in the following table were measured at 0C. Experiment[H2SeO3]0(M)[H+]0(M)[I"]0(M)Initial Rate [mol/(L·s)]11.00 x 10-42.00 x 10-23.00 x 10-25.30 x 10-722.00 x 10-42.00 x 10-23.00 x 10-21.06 x 10-633.00 x 10-44.00 x 10-23.00 x 10-26.36 x 10-643.00 x 10-48.00 x 10-23.00 x 10-22.54 x 10-553.00 x 10-48.00 x 10-26.00 x 10-22.04 x 10-462.00 x 10-42.00 x 10-26.00 x 10-28.48 x 10-6What is the rate constant for this reaction?A) 1.5 x 104L5/(mol5·s)B) 1.5 x 1010L5/(mol5·s)C) 4.9 x 105L5/(mol5·s)D) 294 L5/(mol5·s)E) 8.8 L5/(mol5·s)
Q:
For the reaction A + B + C → products, the following initial-rate data were obtained. [A]0(mol/L)[B]0(mol/L)[C]0(mol/L)Initial Rate (mol/(L·s))0.400.400.200.01600.200.400.400.00800.600.100.200.00150.200.100.200.00050.200.200.400.0020What are the reaction orders with respect to A, B, and C, respectively?A) 0, 1, 1B) 1, 2, 1C) 1, 1, 1D) 1, 2, 0E) 0, 2, 1
Q:
Nitrosyl chloride is produced from the reaction of nitrogen monoxide and chlorine:2NO(g) + Cl2(g) → 2NOCl(g)The following initial rates at a given temperature were obtained for the concentrations listed below. ExperimentInitial Rate (mol·L-1·h-1)[NO]0(mol·L-1)[Cl2]0(mol·L-1)12.210.250.25219.890.750.2536.630.250.75From the data, what is the experimental rate law?A) Rate = k[Cl2]B) Rate = k[NO]C) Rate = k[NO][Cl2]2D) Rate = k[NO]2[Cl2]E) Rate = k[NO][Cl2]1/2
Q:
If a reaction is first-order with respect to a particular reactant, when the concentration of that reactant is increased by a factor of 2, the reaction rate will _____.
A) increase by a factor of 2.
B) remain constant.
C) decrease by a factor of .
D) decrease by a factor of .
E) increase by a factor of 4.
Q:
For a certain first-order reaction with the general form aA → products, the rate is 0.32 M·s-1 when the concentration of the reactant is 0.29M. What is the rate constant for this reaction?A) 0.26 s-1B) 1.1 s-1C) 0.32 s-1D) 3.1 s-1E) 3.8 s-1