Question

A first order reaction has a rate constant $1.15\times {10}^{-3}{s}^{-1}$. How long will $5g$ of this reactant take to reduce to $3g$?

• A. $444s$
• B. $400s$
• C. $528s$
• D. $669s$

Answer 1

The correct option is A $444s$

$t=\frac{2.303}{k}\log \frac{\left[R_0\right]}{\left[R\right]}=\frac{2.303}{1.15\times {10}^{-3}}\log \left(\frac{5}{3}\right)$

$=2.00\times {10}^3\log \left(1.667\right)$

$=2\times {10}^3\times 0.2219=444s$.