Problem 77 - Chemistry A Molecular Approach

Question

The iodide ion is a dietary mineral essential to good nutrition. In countries where potassium iodide is added to salt, iodine deficiency (or goiter) has been almost completely eliminated. The recommended daily allowance (RDA) for iodine is \(150 \mu \mathrm{g} /\) day. How much potassium iodide (76.45\% I) should you consume if you want to meet the RDA?

Step-by-Step Solution

Answer

You should consume approximately 0.1962 mg of potassium iodide to meet the RDA for iodine.

Step 1: Determine the Amount of Iodine Required

First, note the RDA for iodine is 150 micrograms (or 0.150 milligrams since 1 microgram is 0.001 milligrams). This is the amount of pure iodine needed.

Step 2: Convert Percentage to a Decimal

Convert the percentage of iodine in potassium iodide to a decimal for calculation purposes. 76.45% can be written as 0.7645.

Step 3: Calculate the Amount of Potassium Iodide Needed

To find out how much potassium iodide is required to get the RDA of iodine, divide the RDA of iodine by the decimal representing the percentage of iodine in potassium iodide. The calculation is as follows: \( \text{Amount of potassium iodide} = \frac{0.150 \text{ mg}}{0.7645} \).

Step 4: Perform the Division

Divide 0.150 mg by 0.7645 to find the amount of potassium iodide needed to meet the RDA of iodine. This gives \( \text{Amount of potassium iodide} = \frac{0.150}{0.7645} \approx 0.1962 \text{ mg} \).

Key Concepts

Recommended Daily Allowance (RDA)

Understanding what Recommended Daily Allowance (RDA) means is crucial for maintaining a balanced diet and preventing nutritional deficiencies, such as iodine deficiency. The RDA represents the average daily level of intake sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in a particular life stage and gender group. In the case of iodine, the RDA for adults is set at 150 micrograms per day.

This amount has been calculated by health organizations to prevent goiter and other iodine deficiency disorders. When a diet does not meet the RDA for a certain nutrient, supplementation may be necessary to fill the gap. In some instances, like with iodine, this supplementation is standardized, as seen with the fortification of table salt with potassium iodide.

Nutrient Calculation

Nutrient calculation involves converting dietary recommendations into practical intake quantities of various foods or supplements. This process includes several steps, starting with identifying the required amount of a pure nutrient, followed by accounting for its concentration in a given source.

Using iodine as an example, it becomes clear that one must convert micrograms to milligrams as necessary, then factor in how much iodine is present in potassium iodide, a common supplement. From the exercise provided, you see that the necessary calculations begin by noting the RDA (in the proper units) and conclude by incorporating the percentage purity of the nutrient in its source form into the final calculation. Grasping these calculation concepts is essential for proper nutrient intake and avoidance of both deficiency and toxicity.

Potassium Iodide Supplementation

Potassium iodide supplementation is a common strategy to prevent iodine deficiency disorders. Because not all dietary sources contain a significant amount of iodine, and because some soils are low in iodine, leading to produce with inadequate levels, potassium iodide is often added to table salt – a universal ingredient – ensuring a more consistent intake across populations.

To understand how to fulfill the RDA of iodine via supplementation, it's important to be aware of the percentage of iodine in the compound. With potassium iodide, approximately 76.45% of its weight is iodine, meaning a calculation must be done to determine how much potassium iodide will deliver the necessary amount of pure iodine. The exercise example shows a step-by-step breakdown of this process, leading to a clear understanding of how to calculate the required amount of a supplement to meet nutritional needs.