Potassium Iodide Molar Mass

Potassium Iodide Molar Mass (KI) is 166.00 g/mol, and it represents the mass of one mole of potassium iodide molecules. This value is important for calculations in chemistry, especially when you need to convert between mass and the amount of substance (in moles) for reactions involving KI.

1. Significance of Molar Mass in Chemical Reactions

• Stoichiometry: In chemical reactions, the molar mass is used to relate the mass of KI to the number of moles. For example, in a reaction that requires 1 mole of potassium iodide, you would need 166 grams of KI. If you have a certain amount of KI in grams, you can calculate the number of moles by dividing the mass by the molar mass.Moles of KI=Mass (g)Molar Mass (g/mol)Moles of KI=Molar Mass (g/mol)Mass (g)​Example: If you have 83 grams of KI, the number of moles would be:

  83166=0.5 moles16683​=0.5moles

• Balanced Reactions: Molar mass is crucial in determining the reactants and products in a balanced chemical equation. For example, if KI is reacting with other chemicals, knowing the molar mass allows you to calculate the exact amounts needed to react fully with other substances.

2. How Molar Mass Relates to Concentration

• Solutions: In preparing solutions of potassium iodide, the molar mass helps in calculating how much solid KI is needed to achieve a desired molarity (concentration). For instance, to prepare a 1 molar (1 M) solution of KI, you would dissolve 166 grams of KI in enough water to make 1 liter of solution.To calculate the amount of KI for any molarity:

  $$\text{Mass of KI}=\text{Molarity (mol/L)}\times \text{Volume (L)}\times \text{Molar Mass (g/mol)}$$Example: To make 0.5 liters of a 2 M KI solution, you would need:

  $$2\text{mol/L}\times 0.5\text{L}\times 166.00\text{g/mol}=166\text{g}$$

3. KI in Analytical Chemistry

• Titrations: In analytical chemistry, KI is often used in titration reactions, such as redox titrations involving iodine. In these cases, knowing the molar mass helps determine how much KI to use when preparing standard solutions or when calculating the concentration of reactants in the titration.
• Gravimetric Analysis: In gravimetric methods, the molar mass allows you to precisely calculate the amount of iodine released or reacted with KI during the analysis.

4. Molar Mass and Physical Properties

• Diffusion Rate: The molar mass of KI also influences its diffusion rate in solutions. Heavier molecules like KI (166 g/mol) diffuse more slowly than lighter molecules. This can be important in applications like dissolving KI in water or using it in medical or industrial settings.
• Vapor Pressure and Boiling Point: While KI is typically solid at room temperature, molar mass contributes to its relatively high melting (681°C) and boiling points (1,330°C), as compared to lighter salts.

5. Use in Real-Life Calculations

• Radiation Protection: In nuclear emergency kits, the molar mass helps in determining the correct dosage of potassium iodide. For example, a typical dose for thyroid protection in adults is around 130 mg of KI, which corresponds to a specific number of moles based on the molar mass.Number of moles=130 mg166.00 g/mol=0.000783 molNumber of moles=166.00g/mol130mg​=0.000783mol This small amount saturates the thyroid gland with stable iodine, protecting it from absorbing radioactive iodine.