Molecular Physics | Thermodynamics Answers

An ideal gas expands isothermally ( T = 410 K) from a volume of 2.50 l and a

pressure of 7.5 atm to a pressure of 1.0 atm. What is the entropy change for this

process? [Ans = 9.3 J/K]

A nuclear power plant operates at 65% of its maximum theoretical (Carnot)

efficiency between temperatures of 660 0 C and 330 0 C. If the plant produces electric

energy at a rate of 1.2 GW, how much exhaust heat is discharged per hour?

[Ans = 1.4 X 10 13 J/h]

A 3.65-mol sample of an ideal diatomic gas expands adiabatically from a

volume of 0.1210 m 3 to 0.750 m 3 . Initially the pressure was 1.00 atm. Determine:

a) the initial and final temperatures, [Ans = 404 K, 195K]

b) the change in internal energy, [Ans = −1.59 X 10 4 J]

c) the heat lost by the gas, [Ans = take a guess]

d) the work done on the gas [Ans = having guessed part c) right, you should…]

Note. 1.00 atm = 101.3 kPa. Assume no molecular vibration but still use

diatomic adjustment values.

Suppose 2.60 mol of an ideal gas of volume V 1 = 3.50 m 3 at T 1 = 290 K is

allowed to expand isothermally to V 2 = 7.00 m 3 at T 2 = 290 K. Determine:

a) the work done by the gas, [Ans = 4,350 J]

b) the heat added to the gas, and [Ans = take a guess]

c) the change in internal energy of the gas. [Ans = check definition of iso…]

A gas is enclosed in a cylinder fitted with a light frictionless piston and

maintained at atmospheric pressure. When 1250 kcal of heat is added to the gas, the

volume is observed to increase slowly from 12.0 m 3 to 18.2 m 3 . Calculate:

a) the work done by the gas, and [Clue = what type of work is this?]

b) the change in internal energy of the gas. [Clue = as with most questions in this

tutorial, use up the 1 st law of ThermoD, ∆U = Q – W]

Note. 1 kcal = 4.186 kJ

1)Deimos, a satellite of Mars, has an average radius of 6.2 km. If the

gravitational force between Deimos and a 2.0 kg rock at its surface is 2.5 ´10^-2 N, what is the mass of Deimos?

 2. A 2.08 ´ 10⁴ kg meteorite is on exhibit in New York City. Suppose this meteorite and another meteorite are separated by 1.27 ´ 10⁷m (a distance equal to Earth’s average diameter). If the gravitational force between them is 2.88 ´ 10^-16 N, what is the mass of the second meteorite?

 4. In 1989, a cake with a mass of 5.81 ´ 10⁴ kg was baked in Alabama. Suppose a cook stood 25.0 m from the cake. The gravitational force exerted between the cook and the cake was 5.0 ´ 10^-7 N. What was the cook’s mass?

 5. The largest diamond ever found has a mass of 621 g. If the force of gravitational attraction between this diamond and a person with a mass of

65.0 kg is 1.0 ´ 10^-12 N, what is the distance between them?

How fast will a 4 meter long car need to go in order to fit inside of a 3 meter long garage? (Give your answers in terms of c, the speed of light)

A 50-g ice cube at -4

oC is dropped into an insulated container conatining 200mL at 25°CWhen thermal equilibrium is reached, the temperature of water dropped to 9°C. How much heat

is gained by the ice cube ?

A 1-kg metal sample is heated to 90

oC and then dropped into an insulated

container containing 200mL of water at 25

oC. When thermal equilibrium is reached, the

temperature of water rose to 40

oC.

1. What is the final temperature of the metal sample ?

2. What happened after the metal sample is dropped into the beaker?

3. Calculate the Q of the metal sample.

4. Calculate the specific heat capacity of the metal sample.

Superman (who we’ll assume to be 2 meters tall) is flying at 0.8c (80% the speed of light). With proper application of physics, how tall will he appear to be to an outside observer?