CHEM 120 WEEK 8 FINAL EXAM 2 LATEST VERSIONS
ACTUAL EXAM 250 QUESTIONS AND CORRECT
DETAILED ANSWERS WITH RATIONALES (VERIFIED
ANSWERS) |ALREADY GRADED A+
What is the definition of the pascal? - ANSWER: Force (N) = (mass)x(acceleration due
to gravity)
Why is the following statement incorrect: "The volume of a gas is inversely
proportional to its pressure" ? - ANSWER: The volume of a gas is inversely
proportional to its pressure at constant temperature and amount (moles) of gas.
Charles's Law: which quantities and variables are fixed and which are variable? -
ANSWER: V1/T1 = V2/T2
Charles's Law states that at constant pressure, the volume of a fixed amount of gas is
directly proportional to its kelvin temperature. Therefore, pressure is fixed; volume
and temperature are variable.
Avogadro's Law: which quantities and variables are fixed and which are variable? -
ANSWER: V1/n1 = V2/n2
At fixed temperature and pressure, the volume occupied by a gas is directly
proportional to the amount of gas. Therefore, temperature and pressure are fixed;
volume is variable.
Amonton's Law: which quantities and variables are fixed and which are variable? -
ANSWER: P1/T1 = P2/T2
At constant volume, the pressure exerted by a fixed amount of gas is directly
proportional to the kelvin temperature. Therefore, the volume is fixed; pressure and
temperature are variable.
Boyle's Law: which quantities and variables are fixed and which are variable? -
ANSWER: P1V1 = P2V2
At constant temperature and amount of gas, the volume of gas is inversely
proportional to its pressure. Therefore, temperature and moles of gas are fixed; the
volume and pressure are variable.
What happens to the volume if temperature doubles at a fixed pressure? - ANSWER:
Doubles.
,What happens to volume if temperature and amount of gas are fixed? - ANSWER:
Pressure and volume are inversely related. If pressure doubles, volume halves; if
volume doubles, pressure halves.
How to solve any "how much volume/temperature/pressure is needed" problems? -
ANSWER: (P1V1)/nT1 = (P2V2)/nT2
Relationship between gas pressure and amount? - ANSWER: PV=nRT
Why do heat (q) and work (w) have positive values when entering a system and
negative values when leaving it? - ANSWER: The sign of the energy depends on the
perspective of the system. Entering is positive, leaving is negative.
If you feel warm after exercising, have you increased the internal energy of your
body? - ANSWER: No, the energy is transferred to the surroundings.
What is the relationship between work and the change in internal energy in adiabatic
processes? - ANSWER: △U = q(heat) + w(work). Therefore, in an adiabatic process, as
q =0, change in work would be the change in internal energy.
What is an adiabatic process? - ANSWER: a process that involves no heat transfer.
State ways in which the body may increase or decrease in its internal energy. -
ANSWER: Internal energy of the body is increased in work is done to it, and the
internal energy of the body is decreased if it performs work. For example, by eating
food and rubbing hands together, the internal energy of the body may increase.
However, by being in a cold room and losing heat to it or working out decreases the
internal energy of the body.
Example of an object that transforms chemical energy to electrical energy: -
ANSWER: battery
Exothermic or endothermic: water freezing - ANSWER: exothermic (negative)
Exothermic or endothermic: water boiling - ANSWER: endothermic (positive). Heat is
entering the system.
Exothermic or endothermic: food being digested - ANSWER: exothermic (negative)
Exothermic or endothermic: a person running - ANSWER: exothermic (negative)
Exothermic or endothermic: a person growing - ANSWER: endothermic (positive).
Heat is absorbed as food calories, body tissues form
Exothermic or endothermic: wood being chopped - ANSWER: endothermic (positive)
, Exothermic or endothermic: heating with the furnace - ANSWER: exothermic
(negative)
What are the main components of the internal energy of a substance? - ANSWER:
The sum of potential energy sum and kinetic energy sum.
Uk (total) = Uk (translational) + Uk (rotational) + Uk (vibrational)
Up (total) = Up (atom) + Up (bonds)
**the Up (atom) has nuclear, electronic, positional, magnetic, electrical, etc.,
components.
Compare the △U and the △H of the following process: an ideal gas is cooled at
constant pressure. - ANSWER: △H = △U + P△V
Looking at PV/nT = PV/nT law, as temperature decreases, the volume of the gas
should decrease. Therefore, Vfinal - Vinitial would be a negative value, meaning that
P△V is negative. Therefore, △U ends up MORE negative than △H.
Benzene - ANSWER: C6H6
Ethene - ANSWER: C2H4
Methene - ANSWER: CH2
Methanol - ANSWER: CH3OH
It is shown that the molecules are tightly packed initially, then after a phase change
it is more free. Can the sign of the △sysU be predicted? - ANSWER: First off, the q
(heat) of the system is positive as this is an endothermic process. The w (work),
however, is negative because the system has done the work of expansion. Therefore,
the sign of △sysU cannot be predicted as we do not know the magnitude of the q
and w values.
Work equation - ANSWER: W = -P△V
Specific Heat Capacity - ANSWER: Energy required to raise the temperature of 1g of a
substance by 1K
Molar Heat Capacity - ANSWER: Energy required to raise 1 mol of a substance by 1K
How do you calculate the specific heat capacity? What do you need? - ANSWER: We
need its mass, heat change (gain or loss), and its temperature change. The equation
is:
Energy (J) = Mass (kg) x C (specific heat capacity) x △T (℃)
Is the C (specific heat capacity) of a substance intensive or extensive property? -
ANSWER: Extensive property is what cannot be used to identify the substance
because it is easily changed. For example, mass. Intensive property is what can help
ACTUAL EXAM 250 QUESTIONS AND CORRECT
DETAILED ANSWERS WITH RATIONALES (VERIFIED
ANSWERS) |ALREADY GRADED A+
What is the definition of the pascal? - ANSWER: Force (N) = (mass)x(acceleration due
to gravity)
Why is the following statement incorrect: "The volume of a gas is inversely
proportional to its pressure" ? - ANSWER: The volume of a gas is inversely
proportional to its pressure at constant temperature and amount (moles) of gas.
Charles's Law: which quantities and variables are fixed and which are variable? -
ANSWER: V1/T1 = V2/T2
Charles's Law states that at constant pressure, the volume of a fixed amount of gas is
directly proportional to its kelvin temperature. Therefore, pressure is fixed; volume
and temperature are variable.
Avogadro's Law: which quantities and variables are fixed and which are variable? -
ANSWER: V1/n1 = V2/n2
At fixed temperature and pressure, the volume occupied by a gas is directly
proportional to the amount of gas. Therefore, temperature and pressure are fixed;
volume is variable.
Amonton's Law: which quantities and variables are fixed and which are variable? -
ANSWER: P1/T1 = P2/T2
At constant volume, the pressure exerted by a fixed amount of gas is directly
proportional to the kelvin temperature. Therefore, the volume is fixed; pressure and
temperature are variable.
Boyle's Law: which quantities and variables are fixed and which are variable? -
ANSWER: P1V1 = P2V2
At constant temperature and amount of gas, the volume of gas is inversely
proportional to its pressure. Therefore, temperature and moles of gas are fixed; the
volume and pressure are variable.
What happens to the volume if temperature doubles at a fixed pressure? - ANSWER:
Doubles.
,What happens to volume if temperature and amount of gas are fixed? - ANSWER:
Pressure and volume are inversely related. If pressure doubles, volume halves; if
volume doubles, pressure halves.
How to solve any "how much volume/temperature/pressure is needed" problems? -
ANSWER: (P1V1)/nT1 = (P2V2)/nT2
Relationship between gas pressure and amount? - ANSWER: PV=nRT
Why do heat (q) and work (w) have positive values when entering a system and
negative values when leaving it? - ANSWER: The sign of the energy depends on the
perspective of the system. Entering is positive, leaving is negative.
If you feel warm after exercising, have you increased the internal energy of your
body? - ANSWER: No, the energy is transferred to the surroundings.
What is the relationship between work and the change in internal energy in adiabatic
processes? - ANSWER: △U = q(heat) + w(work). Therefore, in an adiabatic process, as
q =0, change in work would be the change in internal energy.
What is an adiabatic process? - ANSWER: a process that involves no heat transfer.
State ways in which the body may increase or decrease in its internal energy. -
ANSWER: Internal energy of the body is increased in work is done to it, and the
internal energy of the body is decreased if it performs work. For example, by eating
food and rubbing hands together, the internal energy of the body may increase.
However, by being in a cold room and losing heat to it or working out decreases the
internal energy of the body.
Example of an object that transforms chemical energy to electrical energy: -
ANSWER: battery
Exothermic or endothermic: water freezing - ANSWER: exothermic (negative)
Exothermic or endothermic: water boiling - ANSWER: endothermic (positive). Heat is
entering the system.
Exothermic or endothermic: food being digested - ANSWER: exothermic (negative)
Exothermic or endothermic: a person running - ANSWER: exothermic (negative)
Exothermic or endothermic: a person growing - ANSWER: endothermic (positive).
Heat is absorbed as food calories, body tissues form
Exothermic or endothermic: wood being chopped - ANSWER: endothermic (positive)
, Exothermic or endothermic: heating with the furnace - ANSWER: exothermic
(negative)
What are the main components of the internal energy of a substance? - ANSWER:
The sum of potential energy sum and kinetic energy sum.
Uk (total) = Uk (translational) + Uk (rotational) + Uk (vibrational)
Up (total) = Up (atom) + Up (bonds)
**the Up (atom) has nuclear, electronic, positional, magnetic, electrical, etc.,
components.
Compare the △U and the △H of the following process: an ideal gas is cooled at
constant pressure. - ANSWER: △H = △U + P△V
Looking at PV/nT = PV/nT law, as temperature decreases, the volume of the gas
should decrease. Therefore, Vfinal - Vinitial would be a negative value, meaning that
P△V is negative. Therefore, △U ends up MORE negative than △H.
Benzene - ANSWER: C6H6
Ethene - ANSWER: C2H4
Methene - ANSWER: CH2
Methanol - ANSWER: CH3OH
It is shown that the molecules are tightly packed initially, then after a phase change
it is more free. Can the sign of the △sysU be predicted? - ANSWER: First off, the q
(heat) of the system is positive as this is an endothermic process. The w (work),
however, is negative because the system has done the work of expansion. Therefore,
the sign of △sysU cannot be predicted as we do not know the magnitude of the q
and w values.
Work equation - ANSWER: W = -P△V
Specific Heat Capacity - ANSWER: Energy required to raise the temperature of 1g of a
substance by 1K
Molar Heat Capacity - ANSWER: Energy required to raise 1 mol of a substance by 1K
How do you calculate the specific heat capacity? What do you need? - ANSWER: We
need its mass, heat change (gain or loss), and its temperature change. The equation
is:
Energy (J) = Mass (kg) x C (specific heat capacity) x △T (℃)
Is the C (specific heat capacity) of a substance intensive or extensive property? -
ANSWER: Extensive property is what cannot be used to identify the substance
because it is easily changed. For example, mass. Intensive property is what can help
