Chemistry for Engineers Homework Answers - Chapter 9

Chapter 9 Homework Questions

An ozone (O₃) molecule is traveling at 1.5 x 10³ m/s. What is its kinetic energy in J?

1.	9.0 x 10-19 J
2.	3.0 x 10-19 J
3.	6.0 x 10-20 J
4.	3.0 x 10-20 J
5.	9.0 x 10-20 J

A weight dropped from a building strikes the ground causing the soil to move back and the dirt particles to vibrate and heat up. This is an example of conversion of (1.)___potential/kinetic__ energy to (2.)____kinetic/potential_ energy.

Thermal energy is directly related to the motion of atoms and molecules of the object in question.

1.	False
2.	True

A gas does 189 J of work while expanding, and at the same time it absorbs 154 J of heat. What is the change in internal energy?

a.	-343
b.	35.0
c.	-35.0
d.	29.1
e.	343

"does work" means it's exothermic, which means it gives out/looses energy = -189J 
absorbs means the opposite, endothermic = +154J 

-189J + 154J = -35J

Thermal decomposition of rail car load of limestone to lime and carbon dioxide requires 1.75 x 10⁶ kJ of heat. Convert this energy to

its equivalent in BTUs. Note: 1 BTU = 252 calories
Express your answer in scientific notation: 1.25 x 10³ = 1.25E3

1kJ=0.94781712 BTU

Which is correct regarding an endothermic reaction?

a.	The reaction does not occur.
b.	The reaction liberates heat.
c.	The enthalpy of the reactants is higher than the enthalpy of the products.
d.	The sign of the deltaH is positive.
e.	The temperature increases when the reaction is carried out in a calorimeter.

A 295-g aluminum engine part at an initial temperature of 3.00°C absorbs 85.0 kJ of heat. What is the final temperature of the part (°C)? 
(c of Al = 0.900 J/g·K)?

a.	–2.68°C
b.	3.32°C
c.	323°C
d.	317°C

85000 J = 295 x 0.900 ( T - 3) 
85000 =265.5 T -796.5 

In a certain process, 750 J of work is done on a system which gives off 195 J of heat. The value of ΔE for the process is

a.	-555 J
b.	750 J
c.	555 J
d.	-195 J
e.	195 J

Calculate q (in kJ) when 978 g of water is heated from 10.8°C to 53.6°C. The specific heat capacity of water is 4.184 J/g.°C. Do not add units to your answer.

 175

An iron piston in a compressor has a mass of 3.62 kg. If the specific heat of iron is 0.449 J/g°C, how much heat is required to raise the temperature of the piston from 12.0°C to 111.0°C?

1.	1.61∗ 105 J
2.	1.61∗102 J
3.	4.35 ∗ 105 J
4.	7.08 ∗108 J

Thermal decomposition of rail car load of limestone to lime and carbon dioxide requires 2.86 x 10⁶ kJ of heat. Convert this energy to

its equivalent in BTUs. Note: 1 BTU = 252 calories
Express your answer in scientific notation: 1.25 x 10³ = 1.25E3

2.71E6

Which of the following is not a state function?

a.	internal energy, E
b.	enthalpy, H
c.	heat change, q
d.	pressure, P
e.	volume, V

As the velocity of moving object doubles, the kinetic energy of the object quadruples.

1.	False
2.	True

Which would decrease the internal energy of your body?

a.	lying in the sun
b.	sitting in an air conditioned classroom where its COLD
c.	taking a hot bath
d.	eating food
e.	None of these

What is the change in internal energy (in J) of a system that absorbs 0.615 kJ of heat from its surroundings and has 0.247 kcal of work done on it?

a.	1.65 x 103 J
b.	–4.15 x 102 J
c.	1.65 J
d.	1.03 x 103 J
e.	-1.65 x 103 J

Thermal decomposition of rail car load of limestone to lime and carbon dioxide requires 9.05 x 10⁶ kJ of heat. Convert this energy to calories. 
Express your answer in scientific notation: 1.25 x 10³ = 1.25E3

0.000 +/- 2% (WORK OUT)

Classify the following processes as exothermic or endothermic: 
boiling of water

a. exothermic
b. endothermic

Calculate q (in kJ) when 761 g of water is heated from 40.3°C to 61.7°C. The specific heat capacity of water is 4.184 J/g.°C. Do not add units to your answer.

68

An iron piston in a compressor has a mass of 3.62 kg. If the specific heat of iron is 0.449 J/g°C, how much heat is required to raise the temperature of the piston from 12.0°C to 111.0°C?

1.	1.61∗102 J
2.	7.08 ∗108 J
3.	4.35 ∗ 105 J
4.	1.61∗ 105 J

An electron accelerated to a velocity of 3.81 × 10³ m/s will have more energy than a proton accelerated to the same velocity.

1.	False
2.	True

The work done by a gas undergoing a volume change against a constant pressure is given by the –P x (Vfinal - Vinitial). A certain gas is compressed in a cylinder by a constant pressure of 9.0 atm from a volume of 35.0 L to 4.00 L. Calculate the work (w) for this process.
1 L-atm = 101.325 J

a.	2.8 x 104 J
b.	1.0 x 104 J
c.	-2.8 x 102 J
d.	-2.8 x 104 J
e.	2.8 x 102 J

A gas is allowed to expand at constant temperature from a volume of 2.0 L to 11.2 L against an external pressure of 0.750 atm. If the gas absorbs 128 J of heat from the surroundings, what are the values of q, w, and ΔE respectively?

a.	128 J, 6.9 J, 135 J
b.	128 J, -6.9 J, 121 J
c.	128 J, 697 J, 825 J
d.	128 J, -697 J, -569 J
e.	-128 J, -6.9 J, -135 J

A hungry engineering student reaches for a favorite granola bar while working on a statics assignment. If the granola bar contains 240 "calories" (food calorie), how much energy (J) is consumed when the bar is eaten?

1.	2.6 ∗106 J
2.	3.1 ∗103 J
3.	1.0 ∗103 J
4.	1.0 ∗106 J

Which is not true for an endothermic reaction?

a.	The temperature of the surroundings decreases.
b.	The enthalpy change for the reaction is positive.
c.	Heat flows from the surroundings into the system.
d.	The products have a lower enthalpy than the reactants.
e.	All of these are true.

What is the kinetic energy of a 22,500 lb truck traveling at 55 mi/hr?

1.	6.2 × 106 J
2.	3.1 × 106 J
3.	3.1 × 103 J
4.	6.2 × 108 J

Energy flow to or from a system can be described as either heat or work.

1.	False
2.	True

Complete combustion of 1.0 metric ton of coal (assuming pure carbon) to gaseous carbon dioxide releases 3.3 x 10¹⁰ J of heat. Convert this energy to

kilocalories

a.	7.9 x 109 kcal
b.	1.4 x 108 kcal
c.	7.9 x 106 kcal
d.	1.4 x 1011 kcal
e.	None of these is within 5% of the correct answer

Which of the following is FALSE?

a.	At constant pressure, the enthalpy change of a system equals the heat lost or gained.
b.	ΔH = ΔE - PΔV
c.	In the reaction, N2(g) + O2(g) => 2NO(g), ΔH = ΔE
d.	ΔH > 0 for 1 mol of CO2 in the process CO2(s) => CO2(g)
e.	The heat change, q p, measured for a reaction in a coffee cup calorimeter equals ΔH.

Calculate q in J when 8.15 g of ice is cooled from -32.°C to -75.1.°C (c_ice = 2.087 J/g·K). Do not enter units.

-733 +/- 4%

A shell fired upwards from an anti-aircraft cannon exhibits there major types of energy: 1. kinetic from its motion 2. potential from its altitude 3. the internal energy of the particles that make it up

True

False

What is the change in internal energy (in J) of a system that releases 675 J of thermal energy to its surroundings and has 525 cal of work done on it?

a.	–150 J
b.	1.52 x 103 J
c.	–2.87 x 103 J
d.	3.64 x 102 J
e.	-3.64 x 102 J

Complete combustion of 1.0 metric ton of coal (assuming it to be pure carbon) to gaseous carbon dioxide releases 3.3 x 10¹⁰ J of heat. Convert this energy to

kilojoules

a.	3.3 x 107 kJ
b.	3.3 x 1013 kJ
c.	3.3 x 108 kJ
d.	3.3 x 1012 kJ
e.	None of these is within 5% of the correct answer

Which is not true for an endothermic reaction?

a.	The temperature of the surroundings decreases.
b.	The enthalpy change for the reaction is positive.
c.	Heat flows from the surroundings into the system.
d.	The products have a lower enthalpy than the reactants.
e.	All of these are true.

Calculate q in J when 9.34 g of ice is cooled from -18.9.°C to -74.3.°C (c_ice = 2.087 J/g·K). Do not enter units.

 -1080 +/- 4%

Energy flow to or from a system can be described as either heat or work.

1.	False
2.	True

A system receives 704 J of heat and delivers 218 J of work to its surroundings. What is the change in internal energy of the system (in J)?

486

Complete combustion of 1.0 metric ton of coal (assuming pure carbon) to gaseous carbon dioxide releases 3.3 x 10¹⁰ J of heat. Convert this energy to kilocalories

a.	7.9 x 109 kcal
b.	1.4 x 108 kcal
c.	7.9 x 106 kcal
d.	1.4 x 1011 kcal
e.	None of these is within 5% of the correct answer

Which of the following is not a state function?

a.	internal energy, E
b.	enthalpy, H
c.	heat change, q
d.	pressure, P
e.	volume, V

What is the final temperature if 9.0 grams of metal (specific heat = 1.00 J/gC) at 58 degrees Celcius receives 295 J of heat from the surroundings?

a.	33
b.	58
c.	91
d.	-25
e.	48

A system receives 425 J of heat and delivers 425 J of work to its surroundings. What is the change in internal energy of the system (in J)?

a.	+425 J
b.	-425 J
c.	+850 J
d.	0 J
e.	-850 J

If Z is a state function, ΔZ depends only on the path along which the change in Z takes place.

True

False

If the specific heat of water is 4.180J_g^-1_c^-1, what mass of water can be heated from 5.0C to 80.0C by 27.0 kJ of heat?

a.	0.0861 g
b.	76.0 g
c.	276 g
d.	86.1 g
e.	8.61 g

What is the kinetic energy of a single He atom traveling at 2.0 × 10⁴ m/s?

1.	6.4 × 10−24 J
2.	2.6 × 10−18 J
3.	7.7 × 10−13 J
4.	1.3 × 10−18 J

Complete combustion of 1.0 metric ton of coal (assuming it to be pure carbon) to gaseous carbon dioxide releases 3.3 x 10¹⁰ J of heat. Convert this energy to

kilojoules

a.	3.3 x 107 kJ
b.	3.3 x 1013 kJ
c.	3.3 x 108 kJ
d.	3.3 x 1012 kJ
e.	None of these is within 5% of the correct answer

A chemical reaction in which the bonds formed have less energy than those broken is referred to as a(n):

1.	systematic reaction
2.	exothermic reaction
3.	inverse reaction
4.	endothermic reaction

The work done by a gas undergoing an expansion against a constant pressure is given by the –P x (Vfinal - Vinitial). A system expands in volume from 2.0 L to 24.5 L at constant temperature. Calculate the work (w) if the expansion occurs against a constant pressure of 5.00 atm. 1 L-am = 101.325 J

a.	-113 J
b.	1.24 x 104 J
c.	-1.14 x 104 J
d.	113 J
e.	1.14 x 104 J

A system releases 255 cal of heat to the surroundings while delivering 428 cal of work. What is the change in internal energy of the system (in cal)?

a.	173 cal
b.	–683 cal
c.	–173 cal
d.	683 cal
e.	None of these is within 5% of the correct answer

Thermal decomposition of 5.0 metric tons of limestone to lime and carbon dioxide requires 9.0 x 10⁶ kJ of heat. Convert this energy to joules

a.	9.0 x 108 J
b.	9.0 x 104 J
c.	9.0 x 103 J
d.	9.0 x 109 J
e.	None of these is within 5% of the correct answer

Which set contains only the FALSE statement(s)in the group below?
a. For the freezing of liquid water ΔH is positive.
b.For a general exothermic reaction ΔH is positive.
c. For the combustion of 1 mol of methane in oxygen ΔH is negative.

a.	a. only
b.	b. only
c.	c. only
d.	a. and b.
e.	a., b., and c.

Calculate q in J when 2.11 g of ice is cooled from -38.3.°C to -60.2.°C (c_ice = 2.087 J/g·K). Do not enter units.

-96