Question

1)A second order reaction has a rate constant of 3.7 M-1min-1. if the initial concentration of the reactant is 0.0100M, what is the concentration remaining after 15 min?
a) .0099M
b) .0056M
c) .0025M
d) .0064M

2) the rate constant for the first order decomposition of A at 500 degrees Celsius is 9.2 x 10 to the negative 3rd powers s-1. How long will it take for 90.8 % of a 0.500M sample of A to decompose
a) 2.5 x 10 to the 4th power s
b) 25.9s
c)1.13x10 to the 2nd power s
d)2.6 x 10 to the 2nd power s

3) from a plot of In k versus 1/T you can determin
a) the rate constant
b) the order of the reaction 
c) the change in enthalpy of the reaction 
d) the activation energy
e) the equilibrium constant

4)the reaction 2A+ B ->D proceeds as follows
step 1 : A + B-> C+ I (slow)
step 2 : A+I -> D (fast)
what is the rate law for the overall reaction?
a) rate = k [A][B]
b) RATE =k [A]2[B]
c)RATE =k [A]2
d)RATE =k [A][B][C]
e) none of these

Answer 1

1) d

2) d

3) d, because the slope gives the value of Ea / R and here we can get Ea.

4) a, rate=k[A][B]. Since step 1 is the rate-determining step, the rate law is

Since both A and B are reactants, this is the rate law for the reaction.

Addition of 1 and 2 gives the overall reaction, but the step 2 does not affect the rate law because is fast. Note that the rate law is not derived from the overall equation either.