1. Suppose we fill a sealed flask with 0.250 mol of gas A, which then completely
ID: 489891 • Letter: 1
Question
1. Suppose we fill a sealed flask with 0.250 mol of gas A, which then completely reacts to form a second gas, B, according to the reaction: A 2B. At various times during the reaction, we measure the amount of B in the flask and get the following data:
Time (s)
0.00
30.0
60.0
90.0
120
Moles of B
0.000
0.167
0.278
0.350
0.400
a. Calculate the number of moles of A remaining in the flask at each time in the table.
b. Calculate the average rate of disappearance of A for each interval in the table, in units of mol/s. (show work)
Time (s)
0.00
30.0
60.0
90.0
120
Moles of B
0.000
0.167
0.278
0.350
0.400
Explanation / Answer
A = 2B
mol of A remaning
mol of A1 = Ainitial - 1/2*B = 0.25 - 1/2*0.00 = 0.25
mol of A2 = Ainitial - 1/2*B = 0.25 - 1/2*0.167= 0.1665
mol of A3 = Ainitial - 1/2*B = 0.25 - 1/2*0.278= 0.111
mol of A4 = Ainitial - 1/2*B = 0.25 - 1/2*0.35= 0.075
mol of A5 = Ainitial - 1/2*B = 0.25 - 1/2*0.40= 0.05
b)=
average rate of diss. of A in each interval
dC/dT = Ai+1 - Ai / (ti+1 - ti)
dC1/dT =(0.1665-0.25)/(30-0) = -0.002783 M/s
dC2/dT =(0.111 -0.1665)/(60-30) = -0.00185 M/s
dC3/dT =(0.075-0.111 )/(90-60) = -0.0012M/s
dC4/dT =(0.05 -0.075)/(120-90) = -0.00083333333M/s
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