If compound A reacts with B following first order kinetics with rate constant $$2.011 \times 10^{-3}$$ s$$^{-1}$$. The time taken by A (in seconds) to reduce from $$7$$ g to $$2$$ g will be ______. (Nearest Integer)
log5 = 0.698, log7 = 0.845, log2 = 0.301

First order reaction A → B with $$k = 2.011 \times 10^{-3}$$ s$$^{-1}$$. Find time for A to reduce from 7 g to 2 g.

First order kinetics formula:

$$t = \frac{2.303}{k}\log\frac{[A]_0}{[A]}$$

$$t = \frac{2.303}{2.011 \times 10^{-3}}\log\frac{7}{2}$$

$$\log\frac{7}{2} = \log 7 - \log 2 = 0.845 - 0.301 = 0.544$$

$$t = \frac{2.303 \times 0.544}{2.011 \times 10^{-3}} = \frac{1.2528}{2.011 \times 10^{-3}} \approx 623$$ s

The time taken is $$\boxed{623}$$ seconds.