(2 pt) 7. How can you distinguish an intermediate from a catalyst in a multi-ste

Question

(2 pt) 7. How can you distinguish an intermediate from a catalyst in a multi-step reaction mechanism?

(1 pt) 8. Calculate the half-life of a substance that decays according to a first-order rate law and has a rate constant of 2.0 x 10-3 s-1.

(1 pt)   9. What is the half-life for the decomposition of O3 when the concentration of O3 is 2.35 x 10-6 M? The rate constant for this second-order reaction is 50.4 M-1hr-1.

(1 pt)   10. Sketch and label an energy profile for a reaction with Ea = 55 kJ and E = 10 kJ/mol.

(1 pt) 11. A reaction involving reactants NO(g) and H2(g) is found to be first order in H2 and second order in NO. Write the rate law for the reaction.

(1 pt) 12. Explain the difference between a normal chemical equation for a chemical reaction and the mechanism of that reaction.

(3 pt) 13. What is molecularity? What is an elementary reaction? How does the molecularity of an elementary reaction relate to its rate law?

(4 pts) 14. If a temperature increase from 20.0°C to 35.0°C triples the rate constant for a reaction, what is the value of the activation energy for the reaction?

Explanation / Answer

Q7

intermediates are consumed, will not show in the copmlete reaction

catalyst will not be consumed, therefore they appear at the end of reaction

Q8

for a first order:

t 1/2 = ln(2) / K

so

t 1/2 = ln(2)/(2*10^-3) = 346.57 seconds

Q9

if second order:

1/A = 1/A0 + kt

A = 1/2*A0 so

2/A0 - 1/A0 = kt

1/A0 = kt

t = 1/(A0*k) = 1/((2.35*10^-6)(50.4))

t = 8443.09 hours

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