A flask is charged with 0.140 mol of A and allowed to react to form B according

Question

A flask is charged with 0.140 mol of A and allowed to react to form B according to the following hypothetical gas-phase reaction.

The following data are collected.

(a) Calculate the number of moles of B at each time in the table.

0 s
  ____ mol

40 s
  ____ mol

80 s
____ mol

120 s
____ mol

160 s
____ mol



(b) Calculate the average rate of disappearance of A for each 40 s interval, in units of mol/s.

0 - 40 s
____ mol/s

40 - 80 s
____ mol/s

80 - 120 s
  ____ mol/s

120 - 160 mol/s

____mol/s

Explanation / Answer

a) Calculate the number of moles of B at each time in the table.

Time(s) n(A) n(B)

. . 0 . . . . . . . . 0.140 . . . . . . 0.000
. 40 . . . . . . . . 0.062 . . . . . . 0,.078
. 80 . . . . . . . . 0.044 . . . . . . 0.095
120 . . . . . . . . 0.031 . . . . . . 0.109
160 . . . . . . . . 0.016 . . . . . . 0.124

b.) Calculate the average rate of disappearance of A for each 40-s interval, in units of mol/s


n(A) / t (at t2) = ( n(A)3 - n(A)1 ) / (t3 - t1)



Time . . . . . . . n(A) . . . . . . . n(B) . . . . . . . . . . . .n(A) / t

. . 0 . . . . . . . . 0.140 . . . . . . 0.000 0
. 40 . . . . . . . . 0.062 . . . . . . 0.078 -0.0004
. 80 . . . . . . . . 0.044 . . . . . . 0.095 -0.001275
120 . . . . . . . . 0.031 . . . . . . 0.109 -0.00195
160 . . . . . . . . 0.016 . . . . . . 0.124 -0.0027

Rate of dissapearance is -ve as the number of moles of reactants decrease.

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