13. A sample of an ideal gas has a volume of 0.500 L at 25 degrees Celsius and 1

Question

13. A sample of an ideal gas has a volume of 0.500 L at 25 degrees Celsius and 1.20 atm pressure. What is its volume at 75 degrees Celsuys and 3.60 atm?

14. In a mixture of N2 and O2 gases, the mol fraction of N2 is found to be 0.700. The total pressure of the mixture is 1.42 atm. What is the partial pressure of the O2 in the mixture?

17. When equal volumes of the following pairs of liquids are mixed thoroughly and allowed to stand, which pair is most likely to separate into two layers?

(a.) ethanol and methanol (b) carbon tetrachloride and methanol (c) hexane and pentane

and why?

20. Which reaction (or reactions) is the heat of the reaction equal to the heat of the formation?

a. 1/2 N2(g)+O2 (g) ---> NO2 (g)   delta H > 0

b. SO2(g)+1/2 O2 (g) ----->SO3 (g)   delta H < 0

22. During combustion 10 grams of ethanl is completely burned to release CO2 and H2O. 296.6 kJ of heat energy was released during combustion. What is the molar enthalpy of the combustion?

Explanation / Answer

13)

Use P1V1/ T1 = P2V2/ T2

so

V2 = P1V1 T2 / P2 T1

V2 = 1.20 x 0.5 x 348 / 3.60 x 298

V2 = 0.1946 L

so the volume is 0.1946 L

14 ) given mol fraction of N2 is 0.7

so

mol fraction of 02 = 1 - 0.7

mol of fraction of 02 = 0.3

we know that

partial pressure of 02 = mol fraction x total pressure

partial pressure of 02 = 0.3 x 1.42

partial pressure of 02 = 0.426 atm

17) (b) carbon tetrachloride and methanol

the reason is that carbon tetrachloride is a non-polar molecule while methanol is a polar one

20) a. 1/2 N2(g)+O2 (g) ---> NO2 (g)   delta H > 0

during heat of formation the comppound should be formed from its corresponding elements

As N02 is formed from its respective elements N2 and 02 ,   the heat of the reaction equal to the heat of the
formation

22) C2H50H + 302 ----> 2C02 + 3H20

molar mass of ethanol = 46 g

given   296.6 kJ energy is released for 10 g

let Y kJ of energy is released for 46 g

Y = 46 x 296.6 /10

Y = 1364.36 kJ

so 1364.36 kJ of energy is released by the combustion of 1 mole of ethanol

so molar enthalpy of combusiton = - 1364.36 kJ

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