The decomposition of NOBr is studied manometrically because the number of moles of gas changes; it cannot be studied colorimetrically because both NOBr and Br2 are reddish-brown. 2NOBr (g) → 2NO (g) + Br2 (g) Use the data below to make the following determinations: (a) the average rate of decomposition of NOBr over the entire experiment. (b) the average rate of decomposition of NOBr between 2.00 and 4.00 seconds. Time (s) [NOBr] (mol/L) 0.00 0.0100 2.00 0.0071 4.00 0.0055 6.00 0.0045 8.00 0.0038 10.00 0.0033 The rates of decomposition of NOBr are

a) The average rate of decomposition of NOBr over the entire reaction is 3.4 x 10⁻⁴ M/s

b) The average rate of decomposition of NOBr between 2.00 and 4.00 seconds is 4 x 10⁻⁴ M/s

Explanation:

The average rate of decomposition of a reactant can be written as follows:

v = - 1/a Δ[A] / Δt

Where

v: average rate of decomposition of A

a: stoichiometric coefficient of reactant A

Δ[A]: variation of the concentration of reactant A

(final concentration of A - initial concentration of A)

Δt: variation of time (final time - initial time)

a) The average rate of the decomposition of NOBr over the entire experiment can be calculated as follows, using this dа ta:

Initial concentration of NOBr: 0.0100 M

Final concentration of NOBr: 0.0033 M

Initial time: 0.00 s

Final time: 10.00 s

Stoichiometric coefficient of NOBr: 2

Then:

v = - 1/2 Δ[NOBr] / Δt

v = - 1/2 (0.0033 M - 0.0100 M) / (10.00 s - 0.00 s) = 3.4 x 10⁻⁴ M/s

b) In the same way, the rate of decomposition can be calculated between the 2.00 and 4.00 seconds:

v = - 1/2 (0.0055 M - 0.0071 M) / (4.00 s - 2.00 s) = 4 x 10⁻⁴ M/s