Chemistry : Gaseous State: Evaluate Yourself

**Evaluate Yourself**

**1. Freon-12, the compound widely
used in the refrigerator system as coolant causes depletion of ozone layer. Now
it has been replaced by eco-friendly compounds. Consider 1.5 dm ^{3}
sample of gaseous Freon at a pressure of 0.3 atm. If the pressure is changed to 1.2 atm. at a constant temperature, what will be the volume of the gas
increased or decreased?**

**Answer:**

Volume of freon (V_{1}) =
1.5 dm^{3}

Pressure (P_{1}) = 0.3
atm

'T' isconstant

P_{2}= 1.2 atm

V_{2}= ?

∴ P_{1}V_{1} = P_{2}V_{2}

=0.375 dm^{3}

∴ Volume decreased from 1.5 dm^{3} to 0.375
dm^{3}

**2. Inside a certain automobile
engine, the volume of air in a cylinder is 0.375 dm ^{3}, when the
pressure is 1.05 atm. When the gas is
compressed to a volume of 0.125 dm^{3}
at the same temperature, what is the pressure of the compressed air?**

**Answer:**

V_{1} = 0.375 dm^{3}

V_{2} = 0.125

P_{1} = 1.05 atm

P_{2} = ?

**'T' -
Constant**

P_{1}V_{1} = P_{2}V_{2}

P_{2} = 3.8 dm^{3}

**3. A sample of gas has a volume of
3.8 dm ^{3} at an unknown temperature. When the sample is submerged in
ice water at 0 °C, its volume gets reduced to 2.27 dm^{3}. What is its
initial temperature?**

**Answer:**

**4. An athlete in a kinesiology
research study has his lung volume of 7.05 dm ^{3} during a deep
inhalation. At this volume the lungs contain 0.312 mole of air. During
exhalation the volume of his lung decreases to 2.35 dm^{3}. How many
moles of air does the athlete exhale during exhalation? (assume pressure and
temperature remain constant)**

**Answer:**

**5. A small bubble rises from the
bottom of a lake where the temperature and pressure are 8° C and 6.4 atm. to the water surface, where the
temperature is 25°C and pressure is 1 atm.
Calculate the final volume in (mL) of the bubble, if its initial volume is 2.1
mL.**

**Answer:**

**6. (a) A mixture of He and O2 were
used in the ‘air’ tanks of underwater divers for deep dives. For a particular
dive 12 dm ^{3} of O_{2} at 298 K, 1 atm. and 46 dm^{3}
of He, at 298 K, 1 atm. were both pumped into a 5 dm^{3} tank.
Calculate the partial pressure of each gas and **

**2KClO _{3}→ 2KCl + 3O_{2}**

**(b) The oxygen gas was collected by
downward displacement of water at 295 K. The total pressure of the mixture is
772 mm of Hg. The vapour pressure of water is 26.7 mm of Hg at 300K. What is
the partial pressure of the oxygen gas?**

**Answer:**

**7. A flammable hydrocarbon gas of
particular volume is found to diffuse through a small hole in 1.5 minutes.
Under the same conditions of temperature and pressure an equal volume of
bromine vapour takes 4.73 min to diffuse through the same hole. Calculate the
molar mass of the unknown gas and suggest what this gas might be, (Given that
molar mass of bromine = 159.8 g/mole)**

**Answer:**

**8. Critical temperature of H _{2}O,
NH_{3}, and CO_{2} are 647.4, 405.5 and 304.2 K, respectively.
When we start cooling from a temperature of 700 K which will liquefy first and
which will liquefy finally? **

**Answer:**

Critical temperature of a gas is
defined as the temperature above which it cannot be ∴
liquified
even at high pressures. When cooling starts from 700 K, H_{2}O will liquify
first, then followed by ammonia and finally carbon dioxide will
liquify.

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