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Chem 1411
Test 2 On Chapters 4, 5 and 6
Oct 25, 2012.
Due on 10/29/2012. NO LATE HAND-INs accepted.
Total Score 50.Answer all questions.
While working on this test remember the following:
1. first write a balanced equation,
2. note down the relationship between the known and unknown components and tabulate them, and,
3. then plug them into the mathematical relationship and then calculate the unknown.
DONT FORGET TO ENSURE THE UNITS ARE MATCHED AND REPORT THE RESULT
WITH THE APPROPRIATE UNITS.
1.Define the following types of reactions with an example for each:
A. acid-base neutralization,
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B.precipitation,
C.combination,
D.decomposition,
E.combustion,
F.displacement, or disproportionation reaction:
2A. A piece of copper metal was added to an aqueous solution of silver nitrate, and within a few minutes it was
observed that a grey crystalline solid formed on surface of the copper. The solution turned a blue color
characteristic of copper(II) ions. Write the balanced chemical equation for this reaction.
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B. If a student measured out 5 g of silver nitrate for the above reaction, determine the theoretical mass of silver
that would be produced.
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C.Calculate the amount of copper that would required to react completely with 5g of silver nitrate.
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3A. Air is a mixture of gases. Defien Dalton’s law of partial pressure and show how this misture of gases
contribute to the total atmospheric pressure.
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B.Gases are sold in large cylinders for laboratory use. What pressure, in atmospheres, will be exerted by 2,500
g of oxygen gas (O2) when stored at 22°C in a 40.0 L cylinder
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C. Calculate the density, in g/L, of N2 gas at 35°C and 0.98 atm pressure.
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D. The mole fraction of oxygen molecules in dry air is 0.2095. What volume of dry air at 1.00 atm and 25°C is
required for burning 1.00 L of hexane (C6H14, density = 0.660 g/mL) completely, yielding carbon dioxide and
water?
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4A. Write the equation which relates the root mean square (rms) velocity of a gas to the temperature:
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B. What is the rms velocity of Ar gas at 25°C? Calculate the kinetic energy of Ar gas at this temperature:
Show your calculations clearly:
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C. A spacecraft is filled with 0.500 atm of O2 and 0.500 atm of He. If there is a very small hole in the side of
this craft such that gas is lost slowly into outer space,
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A) He is lost 2.8 times faster than O2 is lost.
B) He is lost 8 times faster than O2 is lost.
C) He is lost twice as fast as O2 is lost.
D) O2 is lost 2.8 times faster than He is lost.
E) O2 is lost 8 times faster than He is lost.
D At constant pressure, the density of a gas depends on temperature. Does the density increase or decrease as
the temperature increases?
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4A. Define Chemical energy with an example:
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B. In the case of water( means in the liquid state), the chemical energy is due to what two kinds of bonding:
C. Calculate the amount of heat necessary to raise the temperature of 135.0 g of water from 50.4°F to 85.0°F.
The specific heat of water = 4.184 J/g·°C
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5.Given the following information:
S(rhombic) + O2 (g)
S(monoclinic) + O2 (g)
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SO2 (g)
SO2 (g)
Calculate the enthalpy change for the transformation of
S (rhombic)
S (monoclinic)
ΔH0rxn = -296.06 kJ/mol
ΔH0rxn = -296.36 kJ/mol
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6.Benzene (C6H6) burns in air to produce carbon-dioxide and liquid water. Calculate the heat released (in kJ)
per gram of the compound reacted with oxygen. The standard enthalpy of formation of benzene is 49.04 kJ/mol.
[Hint: see pg 258 for information on how to work this problem ]
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7. Calculate the standard enthalpy of formation of cabondisulfide (CS2) from its elements, given that:
C(graphite) + O2
S(rhombic) + O2
CS2(l) + 3O2
CO2 (g)
SO2 (g)
CO2 (g)
ΔH0rxn = -393.5 kJ/mol
ΔH0rxn = -274.4 kJ/mol
+ SO2 (g)
ΔH0rxn = -1073.6 kJ/mol
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