Sabtu, 01 Agustus 2009


Choose the correct answer!

1. Which of the following sets of quantum numbers describes the most easily removed electron in an aluminum atom in its ground state?
a. n = 3, l = 1, ml = -1, ms = -1/2
b. n = 1, l = 0, ml = 0, ms = -1/2
c. n = 4, l = 1, ml = 1, ms = +1/2
d. n = 3, l = 0, ml = 0, ms = +1/2
e. n = 2, l = 1, ml = 0, ms = -1/2

2. The electronic configuration which represents an atom in the excited state is...
a. 1s2 2s2 2p5
b. 1s2 2s2 2p6
c. 1s2 2s2 2p6 3s2
d. 1s2 2s2 2p5 3s1
e. 1s2 2s2 2p6 3s1

3. The position of an element with the electron configuration (Ar) 4s2 3d10 4p3 in the Periodic Table is in the … (…) group, … period, and … block.
a. 5 (VA), 4, s
b. 5 (VB), 4, p
c. 8 (VIIIA), 4, s
d. 15 (VA), 4, p
e. 15 (VB), 4, d

4. If F3 and NH3 molecules are compared one of another, the correct answer about these molecules is ....
a. BF3 is polar
b. NH3 is non polar
c. NH3 has lone pair electron
d. BF3 doesn’t have lone pair electron
e. the hybridization state of NH3 is sp2

5. If you compare the molecules of methane, ammonia, and water, the wrong answer about those molecules is ....
a. each molecule has certain shape
b. the geometry of methane is tetrahedral
c. the hybridization state of H2O is sp3
d. all molecules have the same geometry
e. the molecule shape of ammonia is pyramid

6. One of the following chemical bonds is very weak and is independent of the type of element involved. This chemical bond is ….
a. ionic
b. covalent
c. hydrogen
d. dipole-dipole
e. Van der Waals

7. Which phase change is exothermic? 1. H2O(s) -->H2O(l) 2. H2O(l) -->H2O(s) 3. H2O(s) -->H2O(g) 4. H2O(l) -->H2O(g)

a. 1
b. 2
c. 1 and 2
d. 1 and 3
e. 3 and 4

8. Given the following equations and delta H values, determine the heat of reaction (kJ) at 298 K for the reaction: N2(g) + O2(g) --> 2 NO(g)
4NH3(g)+5O2(g)-->6H2O(l)+4NO(g) H/kJ = -613 4NH3(g) + 3O2(g)-->2N2(g)+6H2O(l) H/kJ = -790
a. +177
b. +89
c. -89
d. -177
e. -1403

9. Which of the following equations represents a reaction that provides the heat of formation of hydrogen peroxide (H2O2)?
a. 2 H2O(l) --> H2O2(l) + H2(g)
b. H2(g) + O2(g) -->H2O2(l)
c. 2 H(g) + 2 O(g) --> H2O2(l)
d. H2O(l) + 1/2 O2(g) --> H2O2(l)
e. 2 H(g) + O2(g) -->H2O2(l)

10. The heats of formation of CO2(g) and H2O(l) are -394 kJ/mole and -285.8 kJ/mole respectively. Using the data for the following combustion
reaction,calculate the heat of formation ofC4H10(g) 2 C4H10(g) + 13 O2(g) --> 8 CO2(g) + 10 H2O(l) H=-5756.1 kJ
a. -149
b. -138
c. -127
d. -115
e. -106

11. A catalyst alters the rate of a chemical
reaction by ....
a. stability the reaction
b. always providing a surface
on which molecules react
c. changing the products formed in the reaction
d. inducing an alternate pathway for the reaction with generally lower
activation energy
e. changing the frequency of collisions between molecules

12. Which of the following is the rate law (differential) of the reaction aA --> B, if reactant A is second order?
a. Rate = k
b. Rate = k[A]
c. Rate = [A]
d. Rate = k[A]2
e. Rate = [A]2

13. If the concentration of a reactant is doubled and the rate of the reaction quadruples, with all other factors which would affect the rate of the reaction
held constant, the order of the reactant is ....
a. zero
b. first
c. second
d. third
e. forth

14. The following rate data were obtained at 25oC for the indicated reaction. What is the rate-law expression for the reaction: 2 A + B --> 4 C?
[A] mol/L [B] mol/L v of C (M/min)
0.10 0.10 2.0 x 10-4
0.20 0.10 8.0 x 10-4
0.40 0.20 2.6 x 10-2

a. rate = k[A]2 [B]2
b. rate = k[A] [B]
c. rate = k[A]2[B]3
d. rate = k[A] [B]2
e. rate = k[A]2[B]

15. What is the rate law
for a reaction mechanism which consists of the following steps : (1) A + B --> C + D (slow) (2) A + C --> E (fast) (3) E + F --> G (fast)
a. Rate = k[A][C]
b. Rate = k[A][B]
c. Rate = k[B][C]
d. Rate = k[A][E]
e. Rate = k[E][F]

16. The collision theory of reaction rates:
I. helps to expose how temperature affects the rate.
II. assumes that the rate depends on the frequency at which reactants collide.
III. assumes that reactants must be in correct orientation to react.
IV. assumes that only collisions with energy above the activation energy are successful.
a. I, II, and III are correct. IV is incorrect.
b. I, III, and IV are correct. II is incorrect.
c. II, III, and IV are correct, I is incorrect.
d. II and IV are correct, I is incorrect.
e. All are correct statements.

17. Identify the INCORRECT statement below regarding chemical equilibrium ….
a. All chemical reactions are, in principle, reversible.
b. Equilibrium is achieved when the forward reaction rate equals the reverse reaction rate.
c. Equilibrium is achieved when the concentration of species become constant.
d. Equilibrium is achieved when the reaction quotient Q equals the equilibrium constant.
e. Equilibrium is achieved when the reactant and product concentrations become equal.

18. Given the reaction: A2B(s) --> A+(aq) + B2-(aq) What is the equilibrium constant expression for the reaction?
a. 2[A+][B2-]
b. 2[A+] + [B2-]
c. [A+]2[B2-]
d. [A+] [B2-]2
e. [A+]2 + [B2-]
19. The reaction A(g) --> B(g) has a K value of 3.2 x 102. At equilibrium, which of the following would be true?
a. [A] = [B] b. [A] < [B] c. [A] > [B] d. [A] > 0 e. [B] = 0

20. If the reaction :
2A(g) + B(g) --> 3C(g) was changed to 3C(g) --> 2A(g) + B(g) at the same conditions, what would the value of KP be? Kc=X
a. X
b. X2
c. 2X
d. 1/X
e. square root of X
21. What will happen to the value of the equilibrium constant for the following reaction if Cl2 is added after equilibrium is established?
4HCl(g)+O2(g) --> 2H2O(g)+Cl2(g) + heat
a. it will decrease b. no change will occur c. it will increase
d. it will decrease 2 x
e. it will increase 2 x
22. Given the reaction at equilibrium:
2 SO2(g) + O2(g) --> 2SO3(g) + heat
The concentration of SO3(g) may be increased by ....
a. decreasing [SO2]
b. decreasing [O2]
c. adding catalyst
d. increasing the pressure
e. increasing the temperature
23. Consider the following equilibrium: 2O2(g) + N2(g) ⇄ N2O4(g)
When 2.0 mol of O2 and 3.0 mol of N2 were placed in a 10.0 L container at 25oC, the value of Kc=0.90. If the same number of moles of reactant were placed in a 5.0 L container at 25oC, the equilibrium constant would be ….
a. 0.011
b. 0.45
c. 0.90
d. 1.20
e. 1.80
24. One mole of gaseous AB is placed in a one liter container. At equilibrium it is 50% dissociated according to the equation shown here: 2AB --> 2A + B2. The equilibrium constant is ….
a. 0.0125
b. 0.025
c. 0.04
d. 0.125
e. 0.25
25. The equilibrium constant Kc for the following reaction at 800oC is 7.14 x 10-2. What is Kp at this temperature? (R = 0.082 L atm/mol K)
2 CO(g) --> C(s) + CO2(g)
a. 5.92 x 102 b. 9.22 x 10-6 c. 7.14 x 10-2 d. 6.29 e. 8.10 x 10-4

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