Answer:
0.0203M
Step-by-step explanation:
We'll use the integrated rate law for second order reactions:
1/[A]=1/[A]initial+kt
[A]initial=0.5M
k=0.1/s
t=200°C but we need in Kelvins
t=200 +273.15K=473.15K
1/[A]=1/[0.5]+[0.1 x 473.15]
1/[A]=49.315M
[A]~0.0203M
Hope it helps:)