chem practice

39. If equal masses of the following compounds undergo complete combustion, which will yield the greatest mass ofCO2?(A) Benzene,C6H6 (B) Cyclohexane, C6H12 (C) Glucose, C6H12O6 (D) Methane

A

47.The potential energy of a system of two atoms as a function of their internuclear distance is shown in the diagram above.Which of the following is true regarding the forces between the atoms when their internuclear distance is x ?(A) The attractive and repulsive forces are balanced, so the atoms will maintain an average internuclear distance x. (B) There is a net repulsive force pushing the atoms apart, so the atoms will move further apart. (C) There is a net attractive force pulling the atoms together, so the atoms will move closer together. (D) It cannot be determined whether the forces between atoms are balanced, attractive, or repulsive because the diagram shows only the potential energy.

A

The O2 (g) produced from the decomposition of the 1.0 L sample of H2O2(aq)is collected in a previously evacuated 10.0 L flask at 300. K. What is the approximate pressure in the flask after 400. s? (For estimation purposes, assume that 1.0 mole of gas in 1.0 L exerts a pressure of 24 atm at 300. K.) (A)1.2 atm (B)2.4 atm (C)12 atm (D)24 atm

A

When Reaction 3 occurs, does the hybridization of the carbon atoms change? (A) Yes; it changes from . is used instead sp to sp2 (B) Yes; it changes from sp to sp3 (C) Yes; it changes from sp2 to sp3 (D) No; it does not change.

A

40. The reaction system represented above is at equilibrium. Which of the following will decrease the amount of CaO(s)in the system? (A) Increasing the volume of the reaction vessel at constant temperature (B) Lowering the temperature of the system (C) Removing some CO2(g)at constant temperature (D) Removing someCaCO3(s)at constant temperature

B

A solution of a salt of a weak acid HY is added to a solution of another weak acid HX. Based on the information given above, which of the following species is the strongest base? (A)HX(aq) (B)Y−(aq) (C)HY(aq) (D)X−(aq)

B

Assume that the bond enthalpies of the oxygen- hydrogen bonds in H2O are not significantly different from those in H2O2. Based on the value of ΔH°of the reaction, which of the following could be the bond enthalpies(in kJ/mol) for the bonds broken and formed in the reaction? O-O in H2O2 O=O in O2 O-H (A)300 500 500 (B)150 500 500 (C)500 300 150 (D)250 300 150

B

The Lewis electron-dot diagrams of the HClO3 molecule and the HClO2molecule are shown above at the left and right, respectively. Which of the following statements identifies the stronger acid and correctly identifies a factor that contributes to its being the stronger acid? (A)HClO3(aq)is the stronger acid because its molecules experience stronger Londondispersion forces. (B)HClO3(aq)is the stronger acid because the additional electronegative oxygen atom on the chlorine atom stabilizes the conjugate base. (C)HClO2(aq)molecules experience weaker London dispersion forces. is the stronger acid because its (D)HClO2(aq)is the stronger acid because the Acid Solution Volume of NaOH Added (mL) A40B75C115D200lone pairs of electrons on the chlorine atom stabilize the conjugate base.

B

The acid-dissociation constants of HC3H5O3(aq) andCH3NH3+(aq)are given in the table above. Which of the following mixtures is a buffer with a pH of approximately 3 ?(A) A mixture of 100. mL of 0.1 M CH3NH3Cl and 50. mL of 0.1 M NaOH (B) A mixture of 100. mL of 0.1 M HC3H5O3 and 50. mL of 0.1 M NaOH (C) A mixture of 100. mL of 0.1 M NaC3H5O3 and 100. mL of 0.1 M NaOH(D) A mixture of 100. mL of 0.1 M CH3NH3Cl and 100. mL of 0.1 M CH3NH2

B

The proposed mechanism can be written in a more general form, as shown above. Species other than Cl can also decompose O3through the same mechanism. Which of the following chemical species is most likely to decompose O3in the upper atmosphere through the above mechanism? (A)He (B)Br (C)N2 (D)O2

B

Which of the following rate laws for the overall reaction corresponds to the proposed mechanism? (A) Rate = k[O3]2 (B) Rate = k[Cl][O3] (C) Rate = k[ClO][o3]2 (D) Rate = k[O2]3/[O3]2

B

Which of the following reaction energy profiles best corresponds to the proposed mechanism?

B

A 1.0 mol sample of X(g)and a 1.0 mol sample of Q(g)are introduced into an evacuated, rigid 10.0 L container and allowed to reach equilibrium at 50°C according to the equation above. At equilibrium, which of the following is true about the concentrations of the gases? (A)[R] = 1/2[Q] (B)[Q] = 1/2[X] (C)[R] = [Z] > [Q] (D)[X] = [Q] = [R] = [Z]

C

Reaction 2 occurs when an excess of 6 M HCl (aq)solution is added to 100 mL of NaOCl (aq) of unknown concentration. If the reaction goes to completion and 0.010 mol of Cl2(g)is produced, then what was the molarity of the NaOCl solution? (A)0.0010 M (B)0.010 M (C)0.10 M(D)1.0 M

C

To maximize the yield in a certain manufacturing process, a solution of a weak monoprotic acid that has a concentration between0.20 M and 0.30 M is required. Four 100. mL samples of the acid at different concentrations are each titrated with a NaOH0.20 M solution. The volume of NaOH needed to reach the end point for each sample is given in the table above. Which solution is the most suitable to maximize the yield? (A) Solution A (B) Solution B (C) Solution C (D) Solution D

C

Ca(OH)2 (s) precipitates when a 1.0 g sample of CaC2(s) is added to 1.0 L of distilled water at room temperature. If a 0.064 g sample of CaC2 (s) (molar mass 64 g/mol) is used instead and all of it reacts, which of the following will occur and why? (the value of Ksp for Ca(OH)2 is 8.0 x 10-8) (A)Ca(OH)2 will precipitate because Q >K sp. (B)Ca(OH)2will precipitate because Q <K sp. (C)Ca(OH)2 will not precipitate because Q >K sp . (D)Ca(OH)2 will not precipitate because Q <K sp

D

In a paper chromatography experiment, a sample of a pigment is separated into two components, X and Y, as shown in the figure above. The surface of the paper is moderately polar. What can be concluded about X and Y based on the experimental results? (A) X has a larger molar mass than Y does. (B) Y has a larger molar mass than X does. (C) X is more polar than Y. (D) Y is more polar than X.

D

In order to determine the order of the reaction represented above, the initial rate of formation of XY2 is measured using different initial values of [X]and [Y]. The results of the experiment are shown in the table below. In trial 2 which of the reactants would be consumed more rapidly, and why? (A) X, because it has a higher molar concentration. (B) X, because the reaction is second order with respect to X. (C) Y, because the reaction is second order with respect to Y. (D) Y, because the rate of disappearance will be double that of X.

D

The diagram above represents the absorption spectrum for a pure molecular substance. Which of the following correctly indicates the type of transition observed for the substance in each of the regions of the absorption spectrum?RegionX Region Y Region Z (A) Molecular vibration Molecular rotation Electronic transition (B)Electronic transition Molecular rotation Molecular vibration (C)Molecular rotation Molecular vibrationElectronic transition (D)Electronic transitionMolecular vibrationMolecular rotation

D