Name ___Mr. Perfect____________________________________ Date ____Sp 16__________
1. Calculate the molarity and osmolarity of a solution containing 2.98 g of magnesium nitrite
dissolved into 2.35 L of water. (4 pts) Mg(NO2)2 → Mg2+ + 2NO2- (3 particles)
𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦 =
𝑚𝑜𝑙
2.98 𝑔 × 116 𝑔
2.37 𝐿
= 𝟏. 𝟎𝟖 𝒙 𝟏𝟎−𝟐 𝒎𝒐𝒍/𝑳
Osmolarity = 3 x 1.08 x 10-2 = 3.2 x 10-2 Osmol
2. Fill in the missing information in the following table: (12 pts)
Symbol
Protons
Neutrons
Electrons
70
Ga
31
39
31
127
Te
52
75
48
+4
At-
85
125
86
-
Bkn+
97
150
95
+2
210
247
Charge
0
3. Name the following compounds: (8 pts)
a.
BaSO4
(Type I, Ionic)
Barium Sulfate
b.
NF3
(Type III, Covalent)
Nitrogen trifluoride
c.
CaH2
(Type I, Ionic)
Calcium Hydride
d.
SF6
(Type III, Covalent)
Sulfur hexafluoride
4. An element has three naturally occurring isotopes with the following masses and abundances:
Isotopic Mass (amu)
Percent Abundance
19.99
90.60
20.99
0.20
21.99
9.20
What is the atomic mass of this element? (6pts)
1st convert percentages to decimal and then calculate the weighted average (Atomic Mass)
Atomic Mass = (19.99 amu)(0.9060) + (20.99 amu)(0.0020) + (21.99 amu)(0.0920) = 20.17 amu
Chemistry 101 Exam 1
Name ___Mr. Perfect____________________________________ Date ____Sp 16__________
5. For each of the following pairs of ions, write the formula of the corresponding compound.
(12 pts)
a. Na+ and SO42b. Ca2+ and CO32c. Fe3+ and O2Na2SO4
CaCO3
Fe2O3
d. Mg2+ and ClO3Mg(ClO3)2
e. NH4+ and NO3NH4NO3
Soluble
Na , K+, Li+, NH4+
NO3Cl-, Br-, ISO42-
Except
+
None
None
Ag+, Pb2+, Hg22+
Ca2+, Ag+, Pb2+, Ba2+
d. Al3+ and ClAlCl3
Insoluble
CO32PO43S2OH-
Except
Group 1A, NH4+
Group 1A, NH4+
Group 1A, NH4+
Group 1A, Ca2+, Ba2+
6. Write the balance molecular equation, complete ionic equation, and net ionic equation for each
of the following aqueous reactions including phase labels. If no reaction occurs (no precipitate),
just write NR after the arrow: (18 pts)
a.
KNO3(aq)
+
CuCl2 (aq) 
N.R.
b.
Li2SO4(aq)
+
2AgNO3(aq) 
2LiNO3(aq)
+
Ag2SO4(s)
2Li+(aq) + 2NO3-(aq) + 2Ag+(aq) + SO42-(aq)  2Li+(aq) + 2NO3-(aq) + Ag2SO4(s)
2Ag+(aq) + SO42-(aq)  Ag2SO4(s)
c.
Na2S(aq)
+
ZnSO4(aq) 
Na2SO4(aq)
+
ZnS(s)
2Na+(aq) + S2-(aq) + Zn2+(aq) + SO42-(aq)  2Na+(aq) + SO42-(aq) + ZnS(s)
Zn2+(aq) + S2-(aq)  ZnS(s)
Chemistry 101 Exam 1
Name ___Mr. Perfect____________________________________ Date ____Sp 16__________
7. Balance the following Redox reactions using the half-reaction method and clearly label the
oxidation and reduction steps. (10 pts)
Mn2+(aq)
a)
+ BiO3-(aq)  MnO4-(aq) + Bi3+(aq)
[acidic]
2 x (4H2O + Mn2+  MnO4- 8H+ + 5e-)
5 x (2e- + 6H+ + BiO3-  Bi3+ 3H2O)
14H+ + 2Mn2+ + 5BiO3-  2MnO4- + 5Bi3+ + 7H2O
Fe2+(aq) + MnO4-(aq)  Fe3+(aq)
b)
+ Mn2+(aq)
[basic]
5e- + 8H+ + MnO4-  Mn2+ + 4H2O
5 x (Fe2+  Fe3+ + e-)
4H2O + MnO4- + 5Fe2+  Mn2+ + 5Fe3+ + 8OH-
8. Draw the Lewis Dot structures for the following elements. Also, pair the elements that are
isoelectronic. (10 pts)
a) Ca2+
b) F-
c) S2-
d) Na+
Isoelectronic
Ca
Isoelectronic
Na
F
Chemistry 101 Exam 1
S
Name ___Mr. Perfect____________________________________ Date ____Sp 16__________
9. Determine the empirical formula for a compound with the following combustion analysis
results: 27.87 % P and 72.13 % S. Hint: Empirical Formula must have whole numbers. (10 pts)
Assume a 100 g sample:
27.87 𝑔 𝑃 ×
𝑚𝑜𝑙
= 0.899 𝑚𝑜𝑙 ÷ 0.899 𝑚𝑜𝑙 = 1
31 𝑔
×
2 = 2
72.13 𝑔 𝑆 ×
𝑚𝑜𝑙
= 2.25 𝑚𝑜𝑙 ÷ 0.899 𝑚𝑜𝑙 = 2.5
32 𝑔
×
2
= 5
Empirical Formula
P2S5
10. How many grams of PbO are required to produce 10.0 g of Pb(OH)Cl? (10 pts)
PbO(s) + NaCl(s) + H2O(l) → Pb(OH)Cl(s) + NaOH(aq)
Equation is balanced
10.0 𝑔 𝑃𝑏(𝑂𝐻)𝐶𝑙 ×
𝑚𝑜𝑙
1 𝑚𝑜𝑙
1 𝑚𝑜𝑙 𝑃𝑏𝑂
223 𝑔
×
×
×
= 𝟖. 𝟔 𝒈 𝑷𝒃𝑶
259 𝑔 1 𝑚𝑜𝑙 1 𝑚𝑜𝑙 𝑃𝑏(𝑂𝐻)𝐶𝑙
𝑚𝑜𝑙
11. Extra Credit. Calculate the mass % of I in strontium iodate. (5 pts)
Sr(IO3)2
%𝐼 =
254
× 100 = 𝟓𝟖. 𝟎 %
438
Chemistry 101 Exam 1