CHEMISTRY 1411, Examination 1
Sep. 24, 2009
Name: -------
Directions: Please answer the following multiple choice questions next to
each number. Show all your work for bonus question and part II questions in
the space provided.
Part 1- Multiple Choice- (3 points each)
____ 1. Which of the following groups represent the alkaline earth metals?
A. Group B
B. Group IA
C. Group IIA
D. Group IVA
------ 2. An elemental ion has 47 protons, 46 electrons, and 61 neutrons.
What isotope is it?
61
61
108
107
A. Ag+
B. Pd -
C. Ag +
------ 3. Which of the following equals 24.0 nm?
A. 2.40 x 10 -8 m
B. 2.40 x 10 -11 cm
C. 2400 um
D. 2.4 pm
------ 4. A temperature of 63 oF is ----------- K.
A. 290 K
B. 304 K
C. 17 K
D. Pd+
D. 326 K
------ 5. The number 1.05 x 10 9 has how many significant figures?
A. 2
B. 3
C. 4
D. 9
------ 6.
30.79 g + 1.678 g + 854 g = ?
A. 881 g
B. 886.5 g
C. 886 g
D. 889g
------ 7. The correct formula for Tin (II) carbonate is:
A. TiCO3
B. SnCO3
C. Ti2CO3
D. Sn(CO3)2
------ 8. What is the number of moles of ammonium chloride in 32.0 g of
ammonium chloride, NH4Cl?
A. 3.15 x 10 23
B. 0.598
C. 4.33 x 10 22
D. 1.89 x 10 24
------ 9.
A.
B.
C.
D.
Which one of the following represents the oxide ion?
OHO2OO22-
------ 10. What is the number of oxygen atoms in 54.68 g of sodium sulfate,
Na2SO4 ? ( Avogadro’s number = 6.02 x 10 23 )
A. 1.244 x 10 23 O atoms
B. 4.976 x 10 23 O atoms
C. 2.195 x 10 24 O atoms
D. 9.273 x 10 23 O atoms
------ 11. Same elements with same atomic numbers but different atomic
mass are called ------- .
A. isobars
B. isomers
C. isotopes
D. representative elements
------ 12. What is the symbol for the atom composed of 78 protons, 117
neutrons, and 76 electrons?
88
195
226
88
22+
2+
A. Sn
B. Pt
C. Ra
D. Sr 2+
50
78
88
38
------ 13. A piece of rock weighs 24.50 g is placed in a graduated cylinder
with 25.0 ml water. The final volume of water rises to 39.0 ml. What
is the density of rock in kg/L ?
A. 1.75
B. 2.00 x 10-2
C. 17.5
D. 1.80
------ 14. What is the name of the compound with the formula ICl3?
A. Iodine (III) chloride
B. Moniodine trichloride
C. Iodine trichloride
D. Indium (III) chloride
------ 15. Which one of the following compounds considered to be
molecular formula?
A. P4O10
B. KCN
C. BaO2
D. PbCl2
------ 16. What is the formula of potassium chlorate?
A. KCl
B. KClO3
C. KClO2
D. K3ClO3
------ 17. Which of the following does not have the correct charge?
A. C2H3O2 (-1)
B. SO4 (-2)
C. NO3 (-1)
D. PO4 (-2)
------ 18. Which of the following is the correct chemical formula for silver
nitrate?
A. Ag3N
B. AgNO2
C. AgNO3
D. Ag2NO3
------ 19. Given (in order) the correct coefficients to balance the following
reaction.
SeO2 (s) + NaOH (aq) --------- Na2SeO3 (aq) + H2O (l)
A. 1,1,1,1
B. 1,2,1,1
C. 2,1,1,1
D. 2,2,1,2
------ 20. Sulfur dioxide reacts with chlorine to produce thionyl chloride and
dichlorine oxide.
SO2 (g) + 2 Cl2 (g) -------- SOCl2 (g) + Cl2O (g)
If 0.800 mol of Cl2 reacts with SO2, how many moles of Cl2O are
formed?
A. 0.800 mol
B. 0.400 mol
C. 0.200 mol
D. 0.100 mol
------ 21. What is the name of the compound (NH4)2S is:
A. Ammonium sulfate
B. Ammonium sulfide
C. Diammonium monosulfur
D. Ammonium sulfite
------ 22. A combination of sand, salt, and water is an example of a
A. homogeneous mixture
B. heterogeneous mixture
C. compound
D. pure substance
------ 23. Water, no matter where it is found, consists of hydrogen and
oxygen combined in a 1: 8 ratio by mass. This is a statement of
A. The law of multiple proportion
B. The law of constant composition
C. The law of conservation of mass
D. None of these
------ 24. The mass percentage of carbon in C6H14N2O2 is:
A. 45.0 %
B. 7.50%
C. 8.22%
D. 49.3%
Part II- Show all your work for complete credit.
1. Percent composition by mass of an organic compound is:
59.0% C, 7.1% H, 26.2% O, 7.7% N
What is its empirical and molecular formula if its molar mass is
183g/mol. (7 pts)
2. Consider the combustion of benzene,
2C6H6 + 15 O2 ------- 12 CO2 + 6 H2O
If 20.0 g of benzene and 20.0 g of O2 reacts together according to the
above reaction:
a.
identify the limiting reagent
b.
how many grams of the excess reagent will remain unsued?
(7pts)
3. Zinc has a density of 446 Ib/ft3. What is the density of zinc in
Kg/in3? 1 Ib= 454g 1ft = 12 in (7pts)
4. For the reaction: 3 Mg(s) + N2 (g) --------- Mg3N2 (s)
a. How many grams of magnesium nitride can be prepared from 3.82 grams
of magnesium?
b. If the actual yield of magnesium nitride is 4.80 grams, what is the percent
yield of magnesium nitride? ( 7 pts)
BONUS question- Show all your work. (10 pts)
Calculate the atomic weight of an element ‘X’ given the following
information:
Isotope
Mass
% abundance
_____________________________________________________________
X-24
23.985042
78.99
X-25
24.985837
10.00
X-26
25.982593
11.01
Based on your answer identify the element by consulting the periodic table.