What is the sum of all of the stoichiometric

4. What is the sum of all of the stoichiometric coefficients when the following equation is
correctly balanced? (Use the smallest possible whole number coefficients. If your equation
includes any coefficients of one, be sure to count those.)
FeCr
2
O
7
+ K
2
CO
3
+ O
2
® K
2
CrO
4
+ Fe
2
O
3
+ CO
2
(A) 9 (B) 15 (C) 24 (D) 42 (E) 31
(5 pts) 5 . What is the concentration of nitrate ions in a solution labeled as 0.0253 M Fe(NO
3
)
3
?
(A) 0.0253 M (B) 0.0759 M (C) 0.0506 M (D) 0.00843 M (E) None of those
(5 pts) 6. What volume of 0.109 M HNO
3
is required to dissolve 2.50 g of solid Ba(OH)
2
?
Ba(OH)
2
(s) + 2 HNO
3
(aq) ® 2 H
2
O(
!
) + Ba(NO
3
)
2
(aq)

NAME:_________________________________
(5 pts) 7. Diborane (B
2
H
6
) can be produced by the following reaction.
3 NaBH
4
(s) + 4 BF
3
(g) ® 2 B
2
H
6
(g) + 3 NaBF
4
(s)
Which of the following reactant mixtures could produce the greatest amount of diborane? (Assume
that the reaction goes to completion with 100% yield.)
© 2018 L.S. Brown
A3
(6 pts) 8. A sample of N
2
gas occupies a volume of 1.25 L at 45.0°C and 0.975 atm. The temperature
and the pressure of the gas are both changed, and as a result the gas expands to a final
volume of 2.75 L. Find the density of the gas at the end of this process.

(5 pts) 9. Ultraviolet light with a frequency of 1.62 ´ 10
15
s
–1
strikes a tungsten metal surface and
electrons with a kinetic energy of 7.20 ´ 10
–19
J are emitted. What is the electron binding
energy for tungsten?
(A) 7.20 ´ 10
–19
J (B) 3.11 ´ 10
–19
J (C) 4.41 ´ 10
–19
J
(D) 3.53 ´ 10
–19
J (E) 6.81 ´ 10
–19
J
Consider the two possible Lewis structures shown below in answering Questions 10 – 14. In
answering the following questions, be sure to consider any additional resonance structures.
(3 pts) 10. Which of these structures would represent an ion?
(3 pts)
A4
© 2018 L.S. Brown