120 ❯ STEP 4. Review the Knowledge You Need to Score High
(c) At STP, the volume of 1 mol of O 2 should be 22.4 L. The volume is greater because
oxygen was not the only gas in the sample. Water vapor was also present. The presence
of the additional gas leads to a larger volume.
You get 1 point for discussing STP and 22.4 L, and 1 point for discussing the pres-
ence of water vapor.
(d) The equation is
2 S(s) + 3 O 2 (g) → 2 SO 3 (g)According to this equation,
(1 mol O 2 ) (2 mol SO 3 /3 mol O 2 ) = 2/3 mol SO 3You get 1 point for the equation and 1 point for the math. You can get 1 total point
if you used an incorrect number of moles of O 2 from an incorrectly balanced equation.
(e) A nonmetal oxide, such as sulfur trioxide, will dissolve in water to produce an acid. This
will get you 1 point. The following balanced chemical equation is worth 1 additional
point:
SO 3 (g) + H 2 O(l) → H 2 SO 4 (aq)
Total your points. There are 10 points possible.❯ Rapid Review
● Kinetic Molecular Theory—Gases are small particles of negligible volume moving in
a random straight-line motion, colliding with the container walls (that is the gas pres-
sure) and with each other. During these collisions, no energy is lost, but energy may be
transferred from one particle to another; the Kelvin temperature is proportional to the
average kinetic energy. There is assumed to be no attraction between the particles.
● Pressure—Know how a barometer operates and the different units used in atmospheric
pressure.
● Boyle’s law—The volume and pressure of a gas are inversely proportional if the tempera-
ture and amount are constant.
● Charles’s law—The volume and temperature of a gas are directly proportional if the
amount and pressure are constant.
● Gay-Lussac’s law—The pressure and temperature of a gas are directly proportional if the
amount and volume are constant.
● Combined gas law—Know how to use the combined gas equation: P 1 V 1 /T 1 = P 2 V 2 /T 2.
● Avogadro’s law—The number of moles and volume of a gas are directly proportional if
the pressure and temperature are constant. Remember that 1 mol of an ideal gas at STP
(1 atm and 0°C) occupies a volume of 22.4 L. Remember that you should not use the
22.4 L unless the gas is at STP.
● Ideal gas equation—Know how to use the ideal gas equation: PV = nRT.
● Dalton’s law—The sum of the partial pressures of the individual gases in a gas mixture
is equal to the total pressure: PTotal = PA + PB + Pc +...