Evaluate Yourself: Gaseous State (Chemistry)

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 Now it has been replaced by eco-friendly compounds.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 dm³ 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 (V₁) = 1.5 dm³

Pressure (P₁) = 0.3 atm

'T' isconstant

P₂= 1.2 atm

V₂= ?

∴ P₁V₁ = P₂V₂

=0.375 dm³

∴ Volume decreased from 1.5 dm³ to 0.375 dm³

2. Inside a certain automobile engine, the volume of air in a cylinder is 0.375 dm³, when the pressure is 1.05 atm. When the gas is compressed to a volume of 0.125 dm³ at the same temperature, what is the pressure of the compressed air?

Answer:

V₁ = 0.375 dm³

V₂ = 0.125

P₁ = 1.05 atm

P₂ = ?

'T' - Constant

P₁V₁ = P₂V₂

P₂ = 3.8 dm³ 

3. A sample of gas has a volume of 3.8 dm³ at an unknown temperature. When the sample is submerged in ice water at 0 °C, its volume gets reduced to 2.27 dm³. What is its initial temperature?

Answer:

4. An athlete in a kinesiology research study has his lung volume of 7.05 dm³ 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 dm³. 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 dm³ of O₂ at 298 K, 1 atm. and 46 dm³ of He, at 298 K, 1 atm. were both pumped into a 5 dm³ tank. Calculate the partial pressure of each gas and the total pressure in the tank at 298 K (b) A sample of solid KClO₃ (potassium chlorate) was heated in a test tube to obtain O₂ according to the reaction

2KClO₃→ 2KCl + 3O₂

(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 H₂O, NH₃, and CO₂ 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,  H₂O  will  liquify  first,  then followed  by ammonia and finally carbon dioxide will liquify.