Houston Community College System
Chemistry 1405
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CHEM 1405
Final Exam (Chapters 1- 10)
PART I – Multiple choice (2 points each)
DIRECTION- Please write your correct choice in the space provided.
1. Which of the following is a basic step in the scientific method?
A) Perform an experiment and collect data
B) Analyze experimental data and propose a hypothesis
C) Test a hypothesis and state a theory or law
D) All of the above.
2. Round off the following measurement to the three significant digits: 107.500g
A) 107g
B) 108g
C) 107.0g
D) 107.4
3. Add 7.77g to 51.665g and round off the sum to the proper significant digits
A) 59.0g
B) 59.4g
C) 59.43g
D) 59.44g
4. Express 0.000000000000000000000000000000010 as an exponential number.
A) 1.0 x 10-10
B) 1.0 x 10-32
C) 1.0 x 10 -33
D) 1.0 x 1032
5. Which of the following is not a branch of chemistry?
A) Analytical Chemistry
C) Physical Chemistry
B) Environmental Chemistry
D) Biological chemistry
6. Which of the following unit factors is derived from: 1 mile = 1760 yards?
A) 1 mile/ 1 yard
B) 1760 miles/ 1 yard
C) 1760 yards/ 1 mile
D) 1760 yard/ 1760 miles
7. The radius of tin atom is 1.41 x 10-8 cm. What is the radius of the atom in nanometers?
1m = 10 9nm, 1m = 102 cm
A) 1.41 x 10-16 nm
B) 1.41 x 10-10 nm
C) 1.41 x 10-4 nm
D) 1.41 x 10-1 nm
8. A glass cylinder contains four separate liquid layers: mercury (d=13.6g/mL), chloroform (d = 1.49g/mL),
acetic acid (d= 1.05g/mL), ether (d = 0.708g/mL). If a marble (d= 3.05g/mL) is added to the cylinder, where
does it come to rest?
A) On top of the mercury layer
C) On top of acetic acid layer
B) On top of chloroform layer
D) On the top of ether layer
9. A 50.0g sample of solid aluminum releases 420.0 calories when cooled from 100.00C to 60.00C.
What is the specific heat of the metal?
A) 0.168 cal/(g x 0C)
B) 0.210 cal/(g x 0C)
C) 0.840 cal/(g x 0C)
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D) 4.76 cal/(g x 0C)
10. Given that methanol freezes at -940C, what is the freezing point temperature on the Kelvin scale?
A) -367K.
B) -179K
C) -94K
D) 179K
11. Which of the following elements is an example of a semimetal?
A) H
B) C
C) Fe
D) Ge
12. Use the periodic table and predict which of the following elements a liquid at 250C is?
A) B
B) Ba
C) Be
D) Br
13. How many neutrons are in the nucleus of one atom of oxygen-18?
A) 2
B) 8
C) 10
D) 18
14. What is the maximum number of electrons that can occupy a 4d sublevel?
A) 4
B) 4
C) 7
D) 10
15. The original periodic law was based on which of the following?
A) Increasing atomic mass
C) Increasing isotopic number
B) Increasing atomic number
D) Increasing mass number.
16. Predict the boiling point for argon given the boiling points of Krypton (-1520C) and Xenon (-1070C)
A) -1970C
B) -1300C
C) -620C
D) -450C
17. What is the core electron configuration for a titanium (II) ion, Ti2+ ?
A) (Ar)
B) (Ar) 4s2.
C) (Ar) 3d2.
D) (Ar) 4s2 3d2.
18. Aqueous HBr is classified as which of the following?
A) Binary ionic
B) Ternary ionic
C) Binary molecular
D) Binary acid.
19. What is the formula for the ionic compound composed of bismuth ion, Bi3+, and CN- ?
A) BiCN
B) BiCN3
C) Bi3CN
D) Bi(CN)3.
20. Which of the following is not evidence for a chemical reaction producing a gas?
A) An odor is detected
C) a flaming splint is extinguished
B) a color change is observed
D) a burning splint bursts into flames
21. What are the products from the following decomposition reaction?
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Co2(CO3)3(s) →
A) Co and CO2
B) CoO and CO2
C) Co2O3 and CO2
D) CoO, H2O, and CO2
22. How many methane molecules, CH4, have a mass of 3.2g?
A) 1.20 x 1023 molecules
B) 1.20 x 1024 molecules C) 1.93 x 10 24 molecules
D) 3.01 x 1023 molecules
23. If 1.00mol of krypton gas exerts a pressure of 1.00 atm at 1000C, what is the volume of the gas?
(R = 0.0821atm.L/mol.K)
A) 2.20mL
B) 8.21 L
C) 12.2L
D) 30.6L
24. How many valence electrons are in a bromine atom and a bromide ion?
A) 1 and 7, respectively
B) 1 and 8, respectively
C)7 and 8, respectively
D) 7 and 10, respectively.
25. Which of the following ions has the following electron configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6?
A) I-
B) S2-
C) K+
D) Sr2+
26. If the electronegativity values for H, N, O, and P are 2.1, 3.0, 3.5, and 2.1, respectively, which of the
following is a nonpolar covalent molecule?
A) water, H2O
B)Laughing gas, N2O
C) phosphine, PH3
D) ammonia, NH3.
27. What is the strongest intermolecular force in a liquid containing polar molecule?
A) Covalent bond
C) Permanent dipole forces
B) Ionic bond
D) Temporary dipole forces
28. What are the products from the complete combustion of a hydrocarbon?
A) Carbon dioxide and water
C) Carbon monoxide and water
B) Carbon monoxide and hydrogen
D) Carbon dioxide and hydrogen
29. What is the systematic name for for Ca(NO3) 2.4H2O
A) Calcium nitrate dihydrate
C) Calcium nitrite dihydrate
B) Calcium nitrate tetrahydrate
D) Calcium nitrite tetrahydrate
30. What is the strongest intermolecular force in a liquid having molecules with H-N bonds?
A) Dipole forces
B) Dispersion forces
C) Hydrogen bond
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D) covalent Bond
PART II – Show your work (8 points for each question) – Please answer in space provided.
1. Perform the following metric-metric conversions.
a) 125 Gm to Mm
b) 255 mg to cg
c) 1 s to ns
d) 1 L to cm3
2. a. A sample of fluorine gas occupies 855 mL at 710 mm Hg and 1550C. What is the mass of the sample?
b. A sample of krypton gas has a volume of 500.0mL at 225mm Hg and -1250C. Calculate the pressure in mm
Hg if the gas occupies 220.0 ml at 1000C
3. a. Calculate the percentage of water, Na2SO4.10H2O and give the name of the hydrate.
b. Calculate the heat required to convert 10.0g of ice at -10.0oC to liquid water at 20.00C. The specific heat of
ice is 0.50 cal/(g x 0C); the heat of fusion for ice is 80.0 cal/g; and the specific heat of water
is 1.00 cal/(g x 0C).
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4 a. Given the electronegativity of the elements below, indicate which of the following are nonpolar covalent
bonds: i) Cl-Cl ii) Cl-N
iii) N-H
iv) H-P
Cl = 3.0 N= 3.0 H= 2.1 P= 2.1
5. a. What is the mass of mercury that can be prepared from 1.25g of cobalt metal? Given:
Co(s) + HgCl2(aq)→ CoCl3(aq) + Hg(l)
b. Verify the conservation of mass law using the molar masses of reactants and products for each substance in the
following balanced equation:
2KNO3(s) → 2KNO2(s) + O2(g)
6. Dioxane is a common solvent for plastics. If the molar mass is 88g/mol and the percentage composition is 54.5%
C, 9.15% H, and 36.3% O, what is the molecular formula of dioxane?
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PART II – Show your work (8 points for each question) – Please answer in space provided.
1.d 2.b 3.b 4.b 5.b 6.c 7.d 8.b 9.b 10.d 11.d 12.d 13.c 14.d 15.a 16.c 17.a 18.c 19.d 20.d
21.b 22.a 23.d 24.c 25.d 26.c 28.a 29.b 30.c
1. a. 1 Mm = 106m, •: 125 Gm = 125 x 109 m
= 125 x 103 Mm
b. 10 mg = 1 cg, •: 255 mg = 25.5 cg
c. 1 s = 1 x 109 ns
d. 1 L = 103 cm3
= 1000 cm3
2 a. PV = n RT where n (number of moles) is m (or mass)/MM(or molar mass)
PV = mRT/MM,
m = PVMM/RT where R= 0.0821 liter atmosphere per degree mole
m = 0.9342 atm x 0.855L x 38 g per mole/ 428 x 0.0821 L atm per deg mole
m = 0.8678 g (approx. 0.87 g)
b.
P1V1/T1 =
P2V2/T2
225 mm Hg x 500 mL/148 = P2 x 220 mL /373
P2 = 1289.78 mm Hg (approx. 1280 mm Hg)
3. a.
% water = 10H2O / Na2SO4.10H2O x 100% = 180 g /332 g x 100%
= 54.22 %
b. Q (Quantity of Heat) = m (mass) x c (specific heat) x Temperature change (tf-ti)
Q from ice to water =Q with specific heat of ice +Q with fusion of ice +Q with specific heat of water
Take precaution with “Q with fusion of ice” which is negative when going from ice to
water and positive when going from water to ice
Q= 10 g x 0.5 cal/g0C x (-10 – 0) 0C + 10 g x -80 cal/g + 10 g x 1 cal/g0C x (0 – 20) 0C
Q from ice to water = -330 cal
Note: Since heat is gained from turning ice to water, Q would be positive.
Q = + 330 cal
4. a. i. Non-polar ii. Non-polar iii. Polar iv. Non-polar
5.a.
Co(s) + HgCl2(aq) →
CoCl3(aq)
58.9 g of Co(s)
Produced
1g
Produced
1.25 g of Co(s)
Produced
1.25 g of Co(s)
Produced
b.
2KNO3(s)
+
Hg(l)
200.6 g of Hg(l)
200.6 g of Hg(l) / 58.9
200.6 g of Hg(l) / 58.9 x 1.25
4.26 g of Hg
→
2KNO2(s)
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+
O2(g)
Conservation of Mass Law states that in any chemical reaction, matter is
neither created nor destroyed but it can be changed from one form to the other.
Therefore using the equation given in 5. b., the total mass from left hand side
(LHS) must be equal to right hand side (RHS).
2KNO3(s) →
2KNO2(s)
+ O2(g)
2(39 g + 14 g + 3(16 g)) = 2(39 g + 14 g + 2(16 g)) + 2 x 16 g
202 g =
202 g
LHS
=
RHS
6. a. C: 54.5 % /12 = 4.54/2.2688 = 2.001(approx. 2)
H: 9.15% /1 = 9.15/2.2688 = 4.033 (approx. 4)
O: 36.3% /16 = 2.2688/2.2688 = 1
Empirical Formula of Dioxane = C2H4O
n (number of moles) = Molar mass / Empirical mass
= 88 g/mol /44 g/mol
=2
Dioxane: n (C2H4O) = (C2H4O)n
= C4H8O2
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