Question

Substance A reacts according to a first order rate law with $k=5.0\times {10}^{-5}{s}^{-1}.$ If the initial conc. of A is $1.0M,$ the initial rate is:

• A. $1\times {10}^{-5}M{s}^{-1}$
• B. $5.0\times {10}^{-5}M{s}^{-1}$
• C. $1\times {10}^{-4}M{s}^{-1}$
• D. $5.0\times {10}^{-4}M{s}^{-1}$

Answer 1

The correct option is B $5.0\times {10}^{-5}M{s}^{-1}$

For a first order reaction, $r=k\left[A\right]$

By putting the given values, $=5\times {10}^{-5}\left[1\right]=5\times {10}^{-5}M{s}^{-1}$