please right out answer neatly. not type out (24 points) The decomposition of hy

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please right out answer neatly. not type out

(24 points) The decomposition of hydrogen sulfide occurs via the following reaction: 2H,S(g) 2H2(g) + S2 (9) At a temperature of 1065 C, this reaction does not go to completion. When 1.00 atm of H2S is put into a 500.0 mL reaction vessel at a temperature of 1065°C, only 24.0% of the H2S decomposes. The volume of the reaction vessel is held constant during the reaction. a. How many moles of H2S are present before the reaction occurs? b. Calculate the partial pressure of each gaseous species in the final reaction mix- ture. c. What is the total pressure of the reaction mixture? d. If we were to put the vessel containing the final reaction mixture in a vacuum and poke a hole in the side of the box, which species would escape from the vessel first? e. If we were to put the vessel containing the final reaction mixture in a classroom and open the vessel, which species would move the farthest in 10 minutes? f. What information would we need to know to calculate AE for the reaction? Page 8

Explanation / Answer

6. Decomposition of H2S

2H2S ---> 2H2 + S2

1. moles of H2S present before the reaction = PV/RT

where,

n = moles of gas

P = 1 atm

V = 500 ml = 0.5 L

R = gas constant

R = 1065 oC + 273 = 1338 K

So,

n = 1 x 0.5/0.0821 x 1338 = 0.00455 mol

b. After the reaction, 24% H2S decomposes

                         2H2S ---> 2H2 + S2

Initial                    1              -        -

Change             -0.24       +0.24  +0.12

Equilibrium         0.76        0.24     0.12

Partial pressure of H2S = 1 - 0.24 = 0.76 atm

Partial pressure of H2 = 2 x 0.12 = 0.24 atm

Partial pressure of S2 = 0.12 atm

c. Total pressure of the vessel after the reaction = 0.76 + 0.24 + 0.12 = 1.12 atm

d. If the vessel was poked in vacuum, the gas which would excape first would be H2 gas. This is according to the root mean square (rms) velocity, which is inversely proportional to the sq.rt. of the molar mass of the gas molecule. So lowest molar mass gas would have highest rms velocity and would escape first, that is H2 gas.

e. If the vessel was opened in a classroom, the fastest moving gas in 10 mins would be H2 gas. Once again this is based on the rms velocity described above.

f. For calculating dE we need Cv, molar heat capacity at constant value. dE is change in internal energy.

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