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- May 9, 2008
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line # [A]
o o rate
1 1 1 1
2 1 2 4
3 2 4 16
Looking at lines 1 and 2, where the concentration of reactant A is held constant, we see that a doubling in the
concentration of B results in a quadrupling of the rate, therefore the reaction is second order with respect to B. We can
now look at lines 2 and 3 (or 1 and 3) to determine the required reaction order. From line 2 to line 3, the concentration of
B is doubled; the reaction rate should thus quadruple due to the influence of the concentration increase of second order
reactant B. We can divide out this quadrupling effect and create a hypothetical line 4:
GENERAL CHEMISTRY SUBJECT TEST 2 ________________________________________________________________
1 1 1 1
2 1 2 4
3 2 4 16
Looking at lines 1 and 2, where the concentration of reactant A is held constant, we see that a doubling in the
concentration of B results in a quadrupling of the rate, therefore the reaction is second order with respect to B. We can
now look at lines 2 and 3 (or 1 and 3) to determine the required reaction order. From line 2 to line 3, the concentration of
B is doubled; the reaction rate should thus quadruple due to the influence of the concentration increase of second order
reactant B. We can divide out this quadrupling effect and create a hypothetical line 4:
GENERAL CHEMISTRY SUBJECT TEST 2 ________________________________________________________________
12
________________________________________________________________________________________ K A P L A N
line # [A]
o o rate
1 1 1 1
2 1 2 4
3 2 4 16
4 2 2 4
From this revision of the experimental data it can be seen (lines 2 and 4) that a doubling of [A] results in no change
1 1 1 1
2 1 2 4
3 2 4 16
4 2 2 4
From this revision of the experimental data it can be seen (lines 2 and 4) that a doubling of [A] results in no change
in the rate, i.e., 2x = 1. Therefore the reaction is zero order with respect to A.
MY QUESTION IS HOW DO U KNOW IN THE HYPOTHEICAL LINE 4 [A] IS 2?
