Mastering chem If the experiment below is run for 60 s, 0.16 mol A remain. Which of the following statements is or are true? At time 0 seconds, a flask contains 1.00 mole of A and 0 moles of B. At 20 seconds, the flask holds 0.54 moles of A and 0.46 moles of B. At 40 seconds, the flask holds 0.3 moles of A and 0.7 moles of B. After 60 s there are 0.84 mol B in the flask. The decrease in the number of moles of A from t1 = 0 to t2 = 20 s is greater than that for t1 = 40 to t2 = 60 s. The average rate for the reaction from t1 = 40 to t2 = 60 s is 7.0×10−3 M/s.

All of the statements are true.

Explanation:

(a) Considering the system mentioned in the equation:-

The sum of total moles in the flask will always be equal to 1 which leads to confirmation of this statement as for 60 secs= 0.16 mol A and 0.84 mol B

(b) 0<t< 20s,  mole A got reduced from 1 mole to 0.54 moles while at 40s to 60s A got decreased from 0.30 moles to 0.16 moles.

0 to 20s is 0.46 (1 - 0.54 = 0.46)mol whereas,

40 to 60s is 0.14 (0.30-.16 = 0.14) mol

(0.46 > 0.14) mol leading this statement to be true as well.

(c) Average rate from t1 = 40 to t2 = 60 s is given by:

which is true as well