intergrated rate law question 78.10 Pyruvic acid is an intermediate in the ferme

Question

intergrated rate law question

78.10 Pyruvic acid is an intermediate in the fermentation of grains. During fermentation the enzyme pyruvate decarboxylase causes the pyruvate ion to release carbon dioxide. In one experi- ment, an aqueous solution of pyruvate ions of volume 200 mL at an initial concentration of 3.23 mmol-L is placed in a sealed, rigid flask of volume 500 mL at 293 K. Because the concentration of the enzyme was kept constant, the reaction was pseudo-first order in pyruvate ion. The elimination of CO2 by the reaction was monitored by measuring the partial pressure of the CO, gas. The pressure of the gas was found to rise from 0 to 100. Pa in 522 s. What ? is the rate constant of the pseudo-first-order reaction

Explanation / Answer

Using ideal gas law we have:

PV = nRT

Putting values:

100*0.0003 = n*8.314*293

Solving we get:

n = 0.0000123 mol = 0.0123 mmol

So, conc of pyruvate ions after 522 s:

A = (3.23*0.2 - 0.0123)/0.2 = 3.1685 mmol

Using first order rate equation:

A = A0*e-(k*t)

Putting values:

3.1685 = 3.23*e-(k*522).

Solving we get:

k = 3.68*10-5 s-1

Hope this helps !

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