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1. Consider the reaction 2H3PO4 yields P2O5+3H2O Using the information in the fo

ID: 988611 • Letter: 1

Question

1. Consider the reaction

2H3PO4 yields P2O5+3H2O

Using the information in the following table, calculate the average rate of formation of P2O5 between 10.0 and 40.0 s.

Time (s)..............P2O5 (M)

0.........................0

10.......................2.50*10^-3

20......................5.50*10^-3

30 ................... 7.30*10^-3

40.....................8.50*10^-3

50 .....................9.10*10^-3

Rate of formation of P2O5 = ?

what is the average rate of decomposition of H3PO4 between 10.0 and 40.0 s?

2. Consider the reaction:

5Br-(aq) + BrO-3(aq) + 6H+(aq) ---> 3Br2(aq) + 3H20(l)

The average rate of consumption of Br- is 1.06 x 10^-4 M/s over the first two minutes. What is the average rate of formation of Br2 during the same time interval?

Rate of formation of Br2 = ?

Explanation / Answer

1) rate = - 1/2 d/dt [H3PO4] = d/dt [P2O5] =  1/3 d/dt [H2O] rate avg = x2-x1/dt2-dt1

rate of formation of  [P2O5] between 10 and 40 = - 1/2 [x40 - x10]/ t40-t10

=- 1/2 [8.50 *10-3 - 2.50*10-3]/40-10 = 6 *10-3/ 30 = 2 *10-2 M sec

as  - 1/2 d/dt [H3PO4] = d/dt [P2O5] putting value we get

rate of decomposition of [H3PO4] =- - 2 * rate of formation of   [P2O5] = 2 * 2 *10-2  M sec = 4 *10-2  M sec

2) rate = - 1/5 d[BR-] / dt ( rate of decomposition of[BR-]) = 1/3 d[BR2]/dt ( rate of formation of [BR2)

rate of formation of Br2 = 3/5 rate of decompositon of Br-

= 3/5* 1.06 x 10^-4 M/s = 6.36 * 10 -5 M sec-1