Question

One milliequivalent of a ferric (III) ion (Fe^+3) is equal to how many millimoles?

a) 55.85 mmol
b) 1 mmol
c) 3 mmol
d) 9 mmol

Answer 1

One milliequivalent of a Fe+3 ion is equal to 0.333 millimoles, as the ferric ion has a valency of 3. Thus, the correct answer is (b) 1 mmol.

Step-by-step explanation:

To determine the equivalent relationship between milliequivalents and millimoles for a ferric (III) ion (Fe+3), we must consider the valency of the ion. Since the Fe+3 ion has a valency of 3, one equivalent (Eq) of Fe+3 is equal to the amount that would combine with or displace 3 moles of hydrogen ions or other monovalent ions. Therefore, 1 Eq of Fe+3 is equivalent to 1 mole of Fe+3, and 1 milliequivalent (mEq) is equivalent to 1 millimole (mmol) of Fe+3.

The relationship is established by the formulas: 1 mol Fe+3 = 3 Eq Fe+3 and 1 Eq Fe+3 = 1000 mEq Fe+3. To convert milliequivalents to millimoles for a trivalent cation like Fe+3, one would divide the number of milliequivalents by the valency of the ion.

Therefore, one milliequivalent of Fe+3 equals to 1/3 mmol of Fe+3, or approximately 0.333 mmol. So the correct answer to the question would be (b) 1 mmol.