Fall 201S Chemistry 141 Exam 2 Version A Multiple Choice barrier if it has been

Question

Fall 201S Chemistry 141 Exam 2 Version A Multiple Choice barrier if it has been observed that 125 1. How long will it take 10.0 ml of Ne gas to effuse theough a porous barrier if minutes are required for 10.0 ml of Ar gas to effuse theough the same barrier? d. 88.8 min e31.9 min 2 A bulloom is filled with He gas to a volume of 2.10L a 35 "C. The balloon is placed in liquid nitrogen umait its temperature reaches-196 "C. Assuming the pressure remains constant, what is the volurse of the a 8.40L 0.525 1 d. 0.00909 L e-0.375 L The standard eothalpy change for the combustion of I mole of propane is-2043.0 k Calculate Ad for propane based on the following standard molar enthalpies of formation 3. CO(g) -393.5 b. +104.7 k/mol-rxn 4. Carbon monoxide reacts with oxygen to form carbon dioxide In a 1.00 L flask, 4.30 atm of CcO reacts with 2.50 atm of Os. Assuming that the temperature remains constant what is the final pressure in the flask? a 1.80 atm b 2.50 atm c.6.80 atm d. 4.30 atrm e. 4.65 atm 5. Convert 6 18 mm Hg to kPa ( 1 atm = 760 mm Hg-101,3 kPa) a. 4.64 x 10' kPa b0.813 kPa e- 82.4kPa

Explanation / Answer

6) 760 mm Hg = 101.3 kPa

Thus, 618 mm Hg = (101.3*618)/760 = 82.373 kPa

5) 2CO + O2 ---> 2CO2

partial pressure of CO = 4.3 atm

partial pressure of O2 = 2.5 atm

since, temperature and volume remains constant, therefore pressure is directly proportional to moles of the gas

Now, 2 moles of CO reacts with 1 moles of O2 as per the balanced reaction

Therefore, 4.3 moles of CO requires 2.15 moles of O2

Hence CO is the limiting reagent

Thus, moles of CO2 produced = moles of CO reacted = 4.3

moles of O2 unreacted = 2.5-2.15 = 0.35

Hence , total pressure after the reaction = 4.3 + 0.35 = 4.65 atm

4) C3H8 + 5O2 --------> 3CO2 + 4H2O

delta H0rkn = 4*(delta H0f H2O) + 3*(delta H0f CO2) - (delta H0f C3H8)

or, (delta H0f C3H8) = 4*(-241.8) + 3*(-393.5) - (-2043) = -104.7 kJ/mole

3) rate of diffusion is inversely proportional to sqrt(molar mass of the gas)

Thus, rateAr/rateNe = sqrt(molar mass of Ne/molar mass of Ar)

or, TimeNe/TimeAr = sqrt(20/39.95)

or, timeNe = 88.84 minutes

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