Chemical Principles I, First Exam
Name:______________________________
All calculations must be CLEARLY shown to receive ANY credit for questions.
1. (4 pts) Carry out the following operations.
a.
2.453 + 13.21 + 0.0268
b.
3.41 – 0.23 x 0.405
15.69
(sig.fig.!)
3.32 (x before -)
2. (4 pts) Indicate the number of significant figures.
a.
0.012030 g 5
b.
8.06600 mL 6
3. (4 pts) Convert a density of 1.1700 g/cm3 into kg/mm3. Show calculations.
10 mm = 1 cm cubing both sides: (103 mm3 = 13 cm3)
1 kg = 1000 g
1.1700 g x
kg x 13 cm3 = 1.1700 x 10-6 kg/mm3 (really dense stuff!)
3
cm
1000 g
103 mm3
4. (6 pts) Give the number of electrons, protons, and neutrons for the following atoms or ions.
(2 pts for e-, p+, n0 correct on each species)
protons
electrons
neutrons
–
81
35 Br
35
36
46
39
19 K
19
18
20
99
43Tc
43
43
56
5. (24 pts) Name the following compounds:
a.
(NH4)2SO4
ammonium sulfate
b.
NiSO46H2O nickel (II) sulfate hexahydrate (Exercise D.13e)
c.
Cu(NO3)2
copper (II) nitrate or cupric nitrate
Test 1, Lectures 1-3, Chemical Principles I, Michaelmas Term ‘08
1
d.
K2CO3
potassium carbonate
e.
Hg2S
mercury (I) sulfide
f.
Fe(OH)3
iron (III) hydroxide or ferric hydroxide
g.
SnCl2
tin (II) chloride or stannous chloride
h.
HClO
hypochlorous acid
i.
NaHSO3
sodium hydrogen sulfite (or bi sulfite)
j.
CH3(CH2)3CH3
k.
Ca(OH)2
calcium hydroxide
l.
NaNO2
sodium nitrite
pentane
6. (24 pts)Write the chemical formulas for the following compounds:
a.
silver oxide
Ag2O
b.
zinc phosphate
Zn3(PO4)2
c.
aluminum sulfate
Al2(SO4)3
d.
sodium hypochlorite NaClO
e.
lithium sulfate
f.
nitric acid
g.
carbonic acid H2CO3
h.
calcium hydroxide
i.
butane
j.
aluminum oxide
k.
sodium dihydrogen phosphate
l.
potassium cyanide
Li2 SO4
HNO3
Ca(OH)2
CH3(CH2)2CH3
or
CH3CH2CH2CH3
Al2O3
NaH2PO4
KCN
Test 1, Lectures 1-3, Chemical Principles I, Michaelmas Term ‘08
2
7.
(10 pts) Balance the following equations:
a.
Fe2P
+
S
P4S10
+
FeS
Exercise H.5d
Fe2P
+
S
P4S10
+
FeS
FeFe
2
1
PP
1 4
SS
1 11
balance P
4 Fe2P
+
S
P4S10
+
FeS
8
1
4
4
1
11
balance Fe
4 Fe2P
+
S
P4S10
+ 8 FeS
8
8
4
4
1
18
balance S
4 Fe2P
+ 18 S
P4S10
+ 8 FeS
8
8
4
4
18 18
b.
C6H14
+
O2
CO2
+
balanced
H2O
See Example H.1
Test 1, Lectures 1-3, Chemical Principles I, Michaelmas Term ‘08
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8. (16pts) Calculate both the empirical formula and the molecular formula of diazepam dimer,
whose molecular weight (molar mass) is 569.4 g/mol. Analysis of diazepam gives 67.47 % C,
4.60 % H, 5.62 % O, and 9.84 % N, and 12.45 % Cl.
Step 1:
C:
67.47 g C / (12.01 g·(mol C)-1 )= 5.618 mol C
H:
4.60 g H / (1.01 g·(mol H)-1 ) = 4.55 mol H
O:
5.62 g O / (16.00 g·(mol O)-1 ) = 0.351 mol O
N:
9.84 g N / (14.01 g·(mol C)-1 ) = 0.702 mol N
Cl:
12.45 g Cl / (35.45 g·(mol Cl)-1 ) = 0.351 mol Cl
C5.62H4.55O0.35N0.70Cl0.35
Step 2: divide each by 0.35; C16H13ON2Cl = empirical formula
Step 3: calculate FW 16(12.01amu)+13(1.01amu)+1(16.00amu)+2(14.01amu) +1(35.45amu) =
284.7amu
Step 4: MW=n(FW); 569.4amu=n(284.7amu); n=2
Step : MolFormula=n(EmpFormula)= 2(C16H13ON2Cl) = C32H26O2N4Cl2
Test 1, Lectures 1-3, Chemical Principles I, Michaelmas Term ‘08
4
9. The price of food rises with the price of oil. One of the major reasons is because the ammonia
that is used to make fertilizer is made from nitrogen and hydrogen. Nitrogen is taken from air but
the hydrogen comes from oil.
a.
Write a balanced equation for the reaction of nitrogen and hydrogen to produce
ammonia. (3 pts)
Balanced: N2 + 3 H2 2 NH3
b.
Calculate the mass percentage of hydrogen in ammonia. (5 pts)
Formula Weight NH3 = 1(14.01amu) + 3(1.01amu) = 17.04amu
%H = 3H / NH3 x 100% = 3(1.01amu) / 17.04amu x 100 = 17.78%
BONUS: 1) Chrysotile is a silicate mineral that is the main component of asbestos. A
specimen that was displayed in a museum has the formula Mg3(Si2O5)(OH)4.
Demonstrate how this formula is probably one for a pure compound. (+2 pts).
Cations:
Mg: 3(+2) +6
Si: 2(+4) +8
______________
Totals
+14
Anions:
O: 5(-2) -10
OH: 4(-1) -4
______________
-14
BONUS: 2) Detach only the page with the period chart and take it with you. (+1pt)
Test 1, Lectures 1-3, Chemical Principles I, Michaelmas Term ‘08
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