Rabu, 05 Desember 2012

Order reaction

Reaction order is the number of factors that affect the concentration of reactants reaction rate.
Determination of the reaction order can not be derived from the equation but can only be determined by experiment.

A reaction experimentally derived reaction rate expressed by the formula:

v = k (A) (B) 2

The equation implies first-order reaction to a substance A and a second order reaction to a substance B. In keselurahan reaction is third order reaction.

Example question:

From the reaction 2NO (g) + Br 2 (g) 2NOBr (g)

made experiments and obtained the following data:
No. (NO) mol / l (Br 2) mol / l Reaction Speed
mol / 1 / sec
1. 0.1 0.1 12
2. 0.1 0.2 24
3. 0.1 0.3 36
4. 0.2 0.1 48
5. 0.3 0.1 108

question:

a. Determine the order of reaction!
b. Determine the value of k (reaction rate constant)!

Answer:

a. First we suppose that the reaction rate formula is as follows: V = k (NO) x (Br 2) y: so we have to find the value of x den y.
To determine the value of x then we take the data in which the concentration of Br2 is unchanged, ie the data (1) and (4).
From these data the concentration of NO is seen up 2 times while the speed of the reaction is increased 4 times then:

2 x = 4 x = 2 (second-order reaction to NO)

To determine the value of y then we take the data which does not change the concentration of NO is data (1) and (2). From these data the concentration of Br 2 look up 2 times, while the reaction rate rose 2 times, then:

2 y = 2 → y = 1 (first-order reaction to Br 2)

So the reaction rate formula: V = k (NO) 2 (Br 2) (order reaction 3)

b. To determine the value of k we simply take one of the only experimental data such as the data (1), then:

V = k (NO) 2 (Br 2)
12 = k (0.1) 2 (0.1)

k = 12 x 10 3 mol -1 -2 1 2 sec

Tidak ada komentar:

Posting Komentar