Question

Problem 7. The pressure inside a 1.0L balloon at 25 in atmospheres, when the balloon is cooled to -42°C the Combined Gas law). Ans: is the pressure is 745 mmHe What is the pro expands to 2.0 L in volume Problem 8. A sample of nitrogen gas contains the new volume if the P and Tare kept constant, but to 2.5 moles. (Use the Avogadro's law). Ans: V2 ° 2.5 moolume if pleoni O moles in a volume of 3.5 L. Calculars he number of moles of N, is changed TP are contained in 1.5 L? Problem 9. How many moles of air at STP are contam Ans: n, moles the pressure of 0.45 mole of nitrogen gas at 25°C and volume 10.L Problem 10. What is the pressure of 0.45 mole of (Use the ideal Gas law). Ans P - Problem 11. CO2 is added to a cylinder containing O2 at 2.5 atm to give a total pressure 4.0 atm. What is the partial pressure of O, and CO2 in the final mixture? Pco = Ans: Po = Problem 12. Air contains 79% N; and 21% 02. What are the partial pressures of nitrogen and oxygen in the hyperbaric chamber that contains air at 2.5 atm? Ans: PN, POT

Answer 1

Q - 7 ) P1 V1 / T1 = P2 V2 / T2

P2 = ( 745 mmHg ) ( 1 litre ) ( 273 — 42 ) K / ( 298 K ) x ( 2 litre ) = 288.75 mmHg

Q -8 ) V1 / V2 = n1 / n2

V2 = V1 x n2 / n1 = ( 3.5 litre ) x ( 2.5 mol ) / 5 mol = 1.75 litre

Q - 9 ) molar volume at STP = 22.7 Litre

Number of moles of air = 1.5 litre / 22.7 litre mol^—1 = 0.066 mol

Q - 10 ) P = nRT / V

= ( 0.45 mol ) ( 0.0821 litre atm mol^—1 K^—1 ) ( 298 K ) / 10 litre = 1.1 atm

Q -11 ) P ( total ) = P ( O2 ) + P ( CO2)

P ( O2 ) = 2.5 atm

P ( CO2 ) = 4 — 2.5 = 1.5 atm

Q -12 ) mole fraction of N2 = 0.79

partial pressure of N2 = mol fraction x p ( total ) = 0.79 x 2.5 atm = 1.975 atm

partial pressure of O2 = 2.5 — 1.975 = 0.525 atm

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