The reaction CH3NC ? CH3CN is called an isomerization reaction andinvolves the breaking of a C–N bond and subsequent formation of a C–C bond—the reactant andproduct have the same molecular formulas and so are isomers. This reaction has a rate constant of0.46 s–1 at a specific temperature. What is the concentration of CH3NC after 0.20 min if its initialconcentration is 0.10 M?A. 4.0 × 10–4 M B. 7.6 × 10–6 M C. 8.5 × 10–2 MD. 9.1 × 10–2 M E. 2.5 × 10–2 M

Answer

A

Explanation:

CH3NC --> CH3CN

k = 0.46 s–1

In first order reactions, the reaction rate is directly proportional to the reactant concentration and the units of first order rate constants are 1/sec.

So the reaction is a first order reaction.

t = 0.20 min = 12 s ( Converting to seconds multiply the time value by 60)

initial concentration [A]o = 0.10 M

Final Concentration [A]  = ?

Formular relating these parameters is given as;

Making [A] subject of interest, we have';

ln[A] = ln[A]o − kt

In[A] = In(0.10) - (0.46*12)

In[A] = -7.8226

[A] = e^(-7.8226)

[A] = 0.000401

[A] = 4 * 10^-4M

the answer is 303.15 or 303