Question

In question 3. the rate of disappearance of O₂ was monitored. For the same balanced reaction

O₂ (aq) + 2 L-dopaH₂ (aq) ⇌ 2 H₂O + 2 L-dopa_ox

[O2] (mM)	[L-dopaH2] (mM}	rate loss of O2 (mMS-1)
4.2	1.7	1.2x!0-3
6.3	1.7	1.8x10-3
4.2	3.4	2.4x10-3
6.3	3.4	3.6x10-3

and the data from the first row from the table above, what are the expected rates of appearance or disappearance of each chemical?

a. O2 _______________________ b. L-dopa-H2 _________________ c. H2O ______________________ d. L-dopaox ___________________

Answer 1

The reaction is,

O₂ (aq) + 2 L-dopaH₂ (aq) ⇌ 2 H₂O + 2 L-dopa_ox

From the stoichiometric coefficients of the reactants and products, we can state the following relation between the rates of appearance or disappearance of each chemical

- d [O2] / dt = (1/2) x -d [L-dopaH₂ ] / dt = (1/2) x d [H₂O] / dt = (1/2) x d [L-dopa_ox ] / dt

Therefore,

Rate of dissapearance of O2 = - d [O2] / dt = 1.2 x 10^-3 mMS^-1

Rate of dissapearance of L-dopaH₂ = -d [L-dopaH₂ ] / dt = 2 x 1.2 x 10^-3 = 2.4 x 10^-3 mMS^-1

Rate of appearance of H₂O = d [H₂O] / dt = 2 x 1.2 x 10^-3 = 2.4 x 10^-3 mMS^-1

Rate of appearance of L-dopa_ox = d [L-dopa_ox ] / dt = 2 x 1.2 x 10^-3 = 2.4 x 10^-3 mMS^-1