Exam 1 - Gases

What the Student Brings to Exams
  • official UT ID card (with your picture and name on it)
  • a simple scientific calculator (not a graphing calculator)
  • a pencil(s) and eraser
  • memorized formulas in your head - not on paper or anything else
  • nothing else is allowed
What we provide for the Exams
  • A printed copy of the exam (every exam has a unique version number on it).
  • An answer sheet for the exam. This is a bubblesheet for your answers.
  • A separate sheet showing a periodic table of the elements with symbols, atomic number, and atomic weights.
  • Also on that separate sheet will be numerous constants, conversion factors, and common data that is needed to solve exam problems.

What Formulas the Student Should Memorize

The Ideal Gas Law (IGL):


Gas Laws "contained" in the IGL:

Boyle's Law:    \(P_1V_1 = P_2V_2\)    (constant n, T)

Charles' Law:    \(\displaystyle{V_1\over T_1} = {V_2\over T_2}\)    (constant n, P)

Avogadro's Law:    \(\displaystyle{V_1\over n_1} = {V_2\over n_2}\)    (constant P, T)

Gay-Lussac's Law:    \(\displaystyle{P_1\over T_1} = {P_2\over T_2}\)    (constant n, V)

Air Up Your Tires Law:    \(\displaystyle{P_1\over n_1} = {P_2\over n_2}\)    (constant V, T)

Difficult to Do This Law:    \(n_1T_1 = n_2T_2\)    (constant P, V)

(note that you will be tested on the actual relationships of the physical properties and not the scientist's names)

and because density (ρ) is m/V and molar mass (M) is m/n, then you also know the molar mass of an ideal gas via:

\[{M={\rho RT\over P}}\]

Dalton's Law of Partial Pressures
\[P_{\rm total}=P_{\rm A} + P_{\rm B} + P_{\rm C} + \cdots\]

mole fraction of gas A:   \(x_{\rm A}=P_{\rm A}/P_{\rm total}\)

Van der Waal's Equation of State (Gas Model)
\[\left(P+a{n^2 \over V^2}\right)(V-nb)=nRT\]

The average kinetic energy of an ideal gas
\[E_{\rm k} = U = {3\over 2}RT = {1\over 2}mv^2\]

Root mean squared velocity of a gas
\[{v_{\rm rms}=\sqrt{3RT \over M}}\]

Comparing rms velocities of two different gases at the same temperature
\[{{v_1\over v_2}=\sqrt{M_2 \over M_1}}\]

What we provide on the exam cover page

R = 0.08206 L atm/mol K

R = 62.36 L torr/mol K

R = 0.08314 L bar/mol K

R = 8.314 J/mol K

NA = 6.022 × 1023 mol-1

1 atm = 1.01325 × 105 Pa

1 atm = 760 torr

1 atm = 14.7 psi

1 bar = 105 Pa

1 in = 2.54 cm

1 lb = 453.6 g

1 gal = 3.785 L

\(\rho_{\rm water} = 1.00\) g/mL

\(\rho_{\rm mercury} = 13.6\) g/mL