1:31 PM mwsu.mrooms3.net \'11 AT&T; 7 (3 pts) The decomposition of NH3 to N2 and

Question

1:31 PM mwsu.mrooms3.net '11 AT&T; 7 (3 pts) The decomposition of NH3 to N2 and Hz on two different catalytic metal surfaces was Metal 163 197 Osmium Without a catalyst, the activation energy is 335 ki/mol. Which is the better catalyst, and why? At 298 K, how many times faster is the reaction on the W surface, compared to the uncatalyzed reaction? Assume that the frequency factor (A) stays the same in both b. 8. (4 pts) A proposed mechanism for a reaction is given below. a. What is the predicted rate law for this mechanism? b. What is the overall balanced equation for this mechanism c. What are the intermediates in this mechanism?

Explanation / Answer

Q7.

a)

better catalyst must be the one which requires the LEAST energy, so choose Tungsten since Ea is lowest

b)

find how many times faster:

We must plot via ---> Ahrrenius Equation for 1 and several Points

According to Arrhenius, we can relate the rate constants as following:

K = A*exp(-Ea/(RT))

Where:

K = rate constant at Temperature “T”

A = Frequency Factor

E = Activation Energy in J/mol

R = ideal gas constant, 8.314 J/mol-K

T = absolute temperature

Ahrrenius Equation 2 Points

From Ahrrenius equation;

K1 = A*exp(-Ea/(RT1))

K2 = A*exp(-Ea/(RT2))

Note that A and Ea are the same, they do not depend on Temperature ( in the range fo temperature given)

K2/K1 = exp(197/163)

K2/K1 = 3.35

K2 = 3.35*K1

it is 3.35 faster

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