Some test strips for blood glucose meters utilize [Fe(CN)₆]³⁻ as an electron transport mediator for the indirect electrochemical detection of the two-electron oxidation of D-glucose into D-gluconolactone, as shown in the figure below. How many moles of electrons will be detected by the glucose meter if 160 μg of [Fe(CN)₆]³⁻ (molar mass 211.9 g/mol) react in a test strip during a measurement and each [Fe(CN)₆]³⁻ ion reacts only once?

Question

Quizplus · Accepted Answer

11ecba2d_11f1_64c2_a3bf_9384fdc3eaf3_MD0008_00 The molar mass of a compound is the amount of mass contained in 1 mole of the compound (grams per mole) and can be used to convert the mass of a compound to the number of moles of that compound. The stoichiometry (relative proportions) for the reactants and/or products of a particular reaction is given by the mole ratios from a balanced reaction equation. Stoichiometry can also be determined from an electrochemical scheme. Given that 160 μg of [Fe(CN)₆]³⁻ react, the number of moles of [Fe(CN)₆]³⁻ contained in this mass is found by dividing by the molar mass of [Fe(CN)₆]³⁻ (scaled to micrograms): 11ecba2d_11f1_64c3_a3bf_a7662ce1dead_MD0008_00 11ecba2d_11f1_64c4_a3bf_651353828607_MD0008_00 The stoichiometry in the electrochemical scheme shows that for every 2 electrons (e⁻) conveyed to the electrode, the reduction of 2 [Fe(CN)₆]³⁻ ions is required. Therefore, if each [Fe(CN)₆]³⁻ ion reacts only once, the number of moles of [Fe(CN)₆]³⁻ that react is equivalent to the number of moles of electrons detected: 11ecba2d_11f1_64c5_a3bf_b3303e5c67a4_MD0008_00 (Choice A) Using a 1:2 electron:[Fe(CN)₆]³⁻ mole ratio instead of the correct 2:2 ratio yields a result of 0.38 μmol. (Choice C) A value of 1.32 μmol is obtained if the molar mass is mistakenly divided by the mass rather than dividing the mass by the molar mass. (Choice D) A 2:1 electron:[Fe(CN)₆]³⁻ mole ratio used instead of the correct 2:2 ratio yields a result of 1.51 μmol. Educational objective: Given the mass of a compound sample, the number of moles present in the sample can be determined using its molar mass. Relating a known number of moles of a reactant to a balanced reaction equation, mole ratios can be applied to determine the stoichiometry of one chemical species relative to another species in a reaction.

Some Test Strips for Blood Glucose Meters Utilize [Fe(CN)6]3− as an Electron

Some Test Strips for Blood Glucose Meters Utilize [Fe(CN)₆]³⁻ as an Electron