What was the initial concentration of A if k = 8.75 × 10-2 s-1? For the first-order reaction below, the concentration of product B after 24.2 seconds is 0.322 M. A → 2B rate = k[ ?<

0.183 M

Solving: Initial Final A X X -x B 0 2x = 0.322 x= 0.166 lnX/X-0.166 = kt= 8.75 10?-2 24.2 = 2.1175 X/X-0.166 = e2.1175 =8.31 X = 8.31X 1.38 7.31X = 1.38 X = 0.188M 24. For the first-order reaction below, the concentration of product B after 24.2 seconds is 0.322 M. If k = 8.75 10-2 s-1, what was the initial concentration of A? A 2B rate = k[A] a. 0.0341 M b. 0.183 M c. 1.34 M d. 2.68 M e. 29.3 M ln 0.322 M/ [A]0 = 8.75 10-2 s-124.2 s = 2.12 e2.12 = 0.322 M/ [A]0 8.33 = 0.322 M/ [A]0 [A]0 = 0.322 /8.33 = 0.0386 M