For Problems 3 through 6, consider the following reaction: 2 A + 4 B ! C + 4 D T

Question

For Problems 3 through 6, consider the following reaction:
2 A + 4 B ! C + 4 D
The rate law for this reaction was experimentally determined to berate = k[A]2[B]3



3.)What is the reaction order with respect to A?

1. 3
2. 6
3. 3/2
4. 1
5. 2
6. 2/3
7. 5



4.)What is the reaction order with respect to B?

1. 2/3
2. 2
3. 3/2
4. 5
5. 3
6. 6
7. 1


5.)If the initial concentration of A is increased
by a factor of 10 and the initial concentration
of B is simultaneously decreased by a factor
of 5, how will this affect the initial reaction
rate?

1. The rate would be four thirds of what it
was.
2. The rate would be doubled.
3. The new rate would be 1.5 times faster
than before.
4. The rate would be unchanged.
5. None of these answers are correct.
6. The new rate would be 2.5 times faster
than before.
7. The rate would be four fifths of what it
was.
8. The rate would be one sixth of what it
was.



6.)What are the units for the rate constant for
this reaction?

1. kJ/mole
2. M5 per second
3.moles/sec2
4. The units are k.
5. Rate law constants are unitless.
6. (liters per mole-second)6
7. moles per liter
8. moles per second
9. M4seconds1

Explanation / Answer

The rate law for this reaction was experimentally determinedto be rate = k[A]2[B]3 3.) The reaction order with respect to A is second order asnoted by the square of the concentration of A in the ratelaw. Answer is 5. 2 4.) The reaction order with respect to B is third order asnoted by the cubed of the concentration of B in the rate law. Answer is 5. 3 5.) To solve this one, just plug in numbers. Pick anumber for k, and pick a concentration for A and B, and plug theminto the equation. Then, change the concentrations for A andB as the question says. Then take the rate for the changedconcentrations and divide it by the rate for the initialconcentrations. You will get an answer of 0.8. Since4/5 = 0.8, the rate will be four fifths of what it was. Answer is 7. The rate would be four fifths of what itwas. 6.) The units for the rate constant for a reaction that is norder overall aremol1-n·Ln-1·s-1. The reaction is fifth order overall as noted by adding 3 and 2together. So, plug 5 in to the equation above. mol1-5·L5-1·s-1 =mol-4·L4·s-1(Remember mol/L = M) Answer is 9. M-4seconds-1 Hope this helps.

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