Question

a spectrophotometry experiment was conducted for the following reaction, which occurred in a 1.10 cm cuvette. The initial concentration of the blue reaciton was 0.75A(aq) (colorless)+B(aq) (blue)→C(aq) (colorless)+D(aq) (colorless)Absorbance, A Time, t 0.77 0.00s 0.67 30.00s 0.60 60.00sa. Find the molar absorptivity coefficient, a, for the blue reactant.b. Find the initial rate of the reaction.

Answer 1

Answer:

a. 0.933 M⁻¹.cm⁻¹

b. 0.003 M/s

Explanation:

a. The molar absorptivity coefficient (ε) is the ability of 1 mol of the substance to mitigate the light of a wavelength. It means that it's a measure of how strong a substance can absorb radiation. It can be calculated by the absorbance (A), the concentration (c) and the length of the cuvette (l).

ε = A/(c*l)

Thus, at t = 0, for the blue reactant, A = 0.77, c = 0.75 M, l = 1.10 cm.

ε = 0.77/(0.75*1.10)

ε = 0.933 M⁻¹.cm⁻¹

b) The rate of the reaction can be found by the rate of desapering of the blue reactant. Let's find the concnetration when t = 30.00 s:

ε = A/(c*l)

0.933 = 0.67/(c*1.10)

1.10c = 0.67/0.933

1.10c = 0.7181

c = 0.65 M

Thus, the rate is the variation of the concentration divided by the time variation:

r = (0.75 - 0.65)/30

r = 0.003 M/s

Because the coefficient of the blue reactant is 1, the rate of reaction is equal to the rate of disappearing of B, 0.003 M/s.