# For the reaction #2A + B -> 3C#, if the rate of disappearance of #B# is #"0.30 mol/L"cdot"s"#, how do you set up a calculation to determine the rate of disappearance of #A# and appearance of #C#?

##### 1 Answer

For

#2A + B -> 3C# ,

knowing that the rate of disappearance of B is

#(Delta[B])/(Deltat) = -"0.30 M/s"# ,

we just have to check the stoichiometry of the problem. Note that the overall rate of reaction is therefore

Since **twice** as much **one** equivalent of ** twice** the rate of

Therefore:

#-1/2(Delta[A])/(Deltat) = -(Delta[B])/(Deltat)#

Similarly, since **three** equivalents of **three times as quickly** in order to get produced in the same interval of time.

#color(blue)(-1/2(Delta[A])/(Deltat) = -(Delta[B])/(Deltat) = 1/3(Delta[C])/(Deltat))#

Knowing that, you can calculate the rate of disappearance of

Even reactions with large negative

The **activation energy** is high for such reactions, and it is difficult for the molecules to find the opportunity to overcome it. They are simply colliding until a *large enough fraction* of the molecules have sufficient energy to *overcome* the reaction barrier.

Until enough of them do, the reaction does not occur.