Chemistry 114
First Hour Exam
Name:____________
(4 points)
Please show all work for partial credit
1. A few days ago a student was intrigued by the phase diagram for carbon which showed
you could change diamond to a liquid when the pressure is 10 Gpa and the temperature
is 5000K.
A. (3 points) Convert 10 GPa to Pa.
B. (3 points) Convert 10 GPa to Bar.
C. (3 points) Convert 10 GPa to atm.
D. (3 points) Convert 10 GPa to psi.
FYI. At earth’s core the pressure and temperature are estimated to be 330 GPa and
5700K.
2. A really high vacuum instrument can achieve an ultrahigh vacuum of 100 nPa.
Assuming chamber has a volume of 1 liter and is filled with N2 gas at 10 Kelvin and 100
nPa pressure. How many N2 molecules are the chamber.
Don’t Freak out, you can do this. I’ll guide you.
A. (4 points) Convert 100 nPa to Atm
B. (4 points) Calculate moles of gas in a 1 liter volume at this pressure and temperature.
C. (4 points) Convert from moles to molecules
1
3. A 22.42 liter container of N2 gas at STP is connected to a 11.21 liter container of Argon
gas that is also at STP.
A. (4 points) When the two gases are allowed to mix, what is the pressure in the system?
B. (4 points) When the two gases mix, what is the mole fraction of N2 in the system?
C. (4 points) When the two gases mix what is the partial pressure of N2 in the system?
4. Define (or give equations for) the following terms (2 points each):
STP
An Ideal gas
A State function
Enthalpy
Viscosity
Surface tension
2
5. A coffee cup calorimeter contains 95 grams of water. The water is initially at 25.5oC.
When I do a chemical reaction the temperature of the water drops to 20.3 oC.
A. (8 points) If the heat capacity of water is 4.182 J/oC, what it the ÄH for the water in the
calorimeter?
B. (4 points) What is the ÄH for the chemical reaction ?
6. Given the ÄH for the following two reactions:
A(g) 6B(g)
B(g) 6C(g)
ÄH =60 kJ
ÄH= -130 kJ
Calculate the ÄH of the following three reactions:
A. (4 points) 3A(g) 63B(g)
B. (4 points) B(g) 6A(g)
C. (4 points) A(g) 6C(g)
3
7. Calculate ÄH rxn for the reaction Fe2O3 (s) + Al(s) 6Fe(s) + Al2O3(s)
Given that
for Fe2O3(s) is -824.2 kJ/mol
and
for Al2O3(s) is -1675.7 kJ/mol
8a. (3 points)Which compound will have the higher melting point? (Circle one)
NaCl(s)
or
CH3OH
Why?
8b. (3 points) Which compound will have the lower viscosity? (Circle one)
CH3CH3
or
CH3CH2OH
Why?
8c. (3 points) Which compound will have the higher vapor pressure? (Circle one)
Cl2
or
I2
Why?
8d. (3 points) Which compound will have the lower melting point? (Circle one)
H2S
or
H2O
Why?
4
9. Up to 5 points extra credit. In the vacuum of space there are only about 3 molecules
of H2 per cubic meter. Assuming the temperature is 2 Kelvin, what is the pressure in space
in units of atm.
(Hint 1: reverse the process you did in problem 2. Hint 2: a liter is (.1m)3 )
5