28. Which of the following has the greatest bond strength?
(A)B₂
(B)O₂⁻
(C)CN⁻
(D)O₂⁺
(E)H₂

4. Which of the following statements is false? (A)The density of a gas is directly proportional to the external pressure.(B)The density of helium gas is double that of hydrogen gas.(C)The density of a gas is indirectly proportional to the temperature in Kelvin. (D)All gases have the same density at STP.(E) All the statements above are correct.

5. For which one of the following reactions is the value of ∆Ho rxn equal to ∆Ho f for the product? (A)2Ca(s) + O2(g)→ 2CaO(s) (B)C2H2(g) + H2(g)→ C2H4(g) (C) 2C(graphite) + O2(g)→ 2CO(g) (D)3Mg(s) + N2(g)→ Mg3N2(s) (E) None of these

6. A mole of yellow photons of wavelength 527 nm has ________ kJ of energy. (A)165(B)227 (C) 4.56 × 10-46 (D)6.05 × 10-3 (E)527

 7. Using the following data reactions:Calculate the energy of an H–Cl bond.(A)770kJ(B)856 kJ(C)518 kJ (D)487 kJ(E)428 kJ 

9. A salt, MY, crystallizes in a body-centered cubic structure with a Y⁻ anion at each cube corner and an M⁺ cation at the cube center. Assuming that the Y⁻ anions touch each other and the M⁺ cation at the center, and that the radius of Y⁻ is 158 pm, what is the radius of M⁺? (A)65.4 pm(B)116 pm(C)79.0 pm (D)41.1 pm(E)105.3 pm

10. When 0.014 mol of a weak acid HA is dissolved in enough water to make 1.0 L of solution, [H ⁺] is 1.8x10-3 M. Calculate the freezing point of this solution. Assume that the molarity concentration is equal to the molality concentration, and assume ideal behavior. *Kf (H₂O) is 1.86°C∙kg/mol. (A)-0.029°C(B)-0.026°C(C)-0.058°C (D)+0.029°C(E)+0.058°C

11. The kinetics of the reaction A + 3B→ C + 2D were studied and the following results obtained, where the rate law is: -∆[A]/ ∆t = k[A]n [B]m. For a run where [A]0= 1.0x10-3 M and [B]0= 5.0 M, a plot of ln[A] versus t was found to give a straight line with slope = -5.0x10-2 s -1 . For a run where [A]0= 1.0x10-3 M and [B]0= 10.0 M, a plot of ln[A] versus t was found to give a straight line with slope = -7.1x10-2 s -1 . Calculate the value of k (ignore units). (A)11(B)10(C)50 (D)1.1(E)22

12. A possible mechanism for the overall reaction: Br2(g) + 2NO(g)→ 2NOBr(g) : NO(g) + Br2(g) ←→ NOBr2(g) (fast; rate constant for forward reaction is k1 and k-1 for reverse reaction) NOBr2(g) + NO(g)→ 2NOBr2(g) (slow; rate constant is k2) The rate law for formation of NOBr based on this mechanism is rate = ________. (A)k1[NO]½ (B)k1[Br₂]½ (C) (k2k1/k-1)[NO]²[Br₂] (D)(k1/k-1)2[NO]² (E)k2[NOBr2][NO]

13. For the reaction CaCO₃(s) ←→ CaO(s) + CO₂(g), Kp = 1.16 at 800.°C. If a 21.1 gram sample of CaCO₃ is put into a 10.0 L container and heated to 800°C, what percent of the CaCO₃ will react to reach equilibrium? (A)32.3%(B)62.5%(C)83.8% (D)41.9%(E)100.0%

14. What is the pH of a solution prepared by mixing 50.0 mL of 0.300 M HCl with 450.0 mL of 0.400 M HIO₃ ? (Ka of HIO₃ = 0.16) (A)1.52(B)0.80(C)0.72 (D)0.89(E)1.10