Question

The isomerization of cyclopropane to form propene ($C{H}_3-CH=C{H}_2$) is a first order reaction. At 760K, 85% of a sample of cyclopropane changes to propene in 79 min. Calculate the value of the rate constant:

• A. $2.42mi{n}^{-1}$
• B. $3.66\times {10}^{-2}$ $mi{n}^{-1}$
• C. $2.40\times {10}^{-2}$ $mi{n}^{-1}$
• D. $1.04\times {10}^{-2}$ $mi{n}^{-1}$

Answer 1

The correct option is C $2.40\times {10}^{-2}$ $mi{n}^{-1}$

$k=\frac{2.303}{t}log\left[\frac{a}{a-x}\right]$

$k=\frac{2.303}{79}log\left[\frac{a}{a-0.85}\right]$

$k=\frac{2.303}{79}log\left[\frac{1}{0.15}\right]$

$k=0.0240mi{n}^{-1}$