# chemistry

posted by
**JES**
.

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g) →B(g). The following data are

obtained for [ A ] as the reaction proceeds:

Time (s) 1 10 20 30 40

Moles of A 0.124 0.110 0.088 0.073 0.054

how do i solve for B?

for problem 8: also i know how to solve for A but i cant figure out the one below, i tried subtracting

0.088 - 0.073/20 = but its wrong

7) The average rate of appearance of B between 20 s and 30 s is __________ mol/s.

A) +7.3 × 10-3

B) +1.5 × 10-3

C) -7.3 × 10-3

D) +5.0 × 10-4

E) -1.5 × 10-3

7)

8) The average rate disappearance of A between 20 s and 30 s is __________ mol/s.

A) 1.6 × 10-2

B) 0.15

C) 670

D) 1.5 × 10-3

E) 5.0 × 10-4