Problem Set 3
• 1. Standard Temperature and Pressure (STP) is
defined as a temperature of 0.00oC and a
pressure of 100kPa. If the molar mass M of
nitrogen is 14.0 g/mol, find the density
(kg/m3) of nitrogen at STP [5 pts]. Nitrous
Oxide or laughing gas is composed of the
molecule N2O. If the molar mass of oxygen is
16.0g/mol, what is the density of N2O at STP?
[5 pts]
• 2. A hypodermic syringe contains medicine with
the density of water. The barrel has a cross
sectional area A=2.50x10-5m2, and the needle has
a cross sectional area a=1.00x10-8m2. In the
absence of a force on the plunger the pressure
everywhere is 1 atm. A force F magnitude 2.00N
acts on the plunger, making medicine squirt
horizontally from the needle. Determine the
speed of the medicine as it leaves the tip? [10pts]
•
• 3. A long rod, insulated from the
sides is in perfect contact with
boiling water and an ice water
mixture. The rod consists of 1.00m
section of copper and a length L2 of
steel. Both sections have a cross
sectional area of 4.00cm2. The
temperature of the copper/steel
junction is 65.0oC after steady-state
has been setup. (a) How much heat
per second flows from boiling water
to the ice-water mixture? [5pts](b)
What is the length of L2? [5pts]
•
• 4. Two speeding lead bullets, each of mass 5.00 g,
at temperature 20oC, collides head on at speeds
500 m/s each. Assume its a perfectly inelastic
collision and no loss of energy to the atmosphere.
What is the final temperature of the system? [10
pts]
Substance
Latent Heat
Fusion
kJ/kg
Melting
Point
°C
Latent Heat
Vaporization
kJ/kg
Boiling
Point
°C
Lead[9]
23.0
327.5
871
1750
• Heat capacity of lead = 128J/kgoC (assume same
for molten lead)
• 5. Two thermally insulated vessels are connected
by a narrow tube fitted with a valve that is
initially closed. One vessel of volume 16.8L,
contains oxygen at a temperature of 300K and a
pressure of 1.75 atm. The other vessel, of volume
22.4L, also contains oxygen but at a temperature
of 450K and a pressure of 2.25 atm. When the
valve is opened and the temperature and
pressure become uniform, (a) What is the final
temperature? [5 pts] (b) What is the final
Pressure? [5 pts]