What is the molar mass of KI (potassium iodide)?
The Correct Answer and Explanation is:
Correct Answer:
The molar mass of potassium iodide (KI) is 166.0 g/mol.
Detailed Explanation:
The molar mass of a compound is calculated by summing the atomic masses of all the atoms in its chemical formula. Here’s how we calculate the molar mass of potassium iodide (KI):
- Atomic Mass of Potassium (K):
Potassium is an alkali metal with an atomic mass of approximately 39.1 g/mol. - Atomic Mass of Iodine (I):
Iodine is a halogen with an atomic mass of approximately 126.9 g/mol. - Formula of Potassium Iodide (KI):
Potassium iodide is composed of one potassium atom (K) and one iodine atom (I). Therefore, the molar mass of KI is:
[
\text{Molar mass of KI} = \text{Atomic mass of K} + \text{Atomic mass of I}
]
Substituting the values:
[
\text{Molar mass of KI} = 39.1 \, \text{g/mol} + 126.9 \, \text{g/mol} = 166.0 \, \text{g/mol}
]
Why Is Molar Mass Important?
The molar mass is critical in chemistry because it allows us to convert between grams and moles of a substance, which is essential for stoichiometric calculations. For example, if you have 10 grams of KI and want to find out how many moles it represents, you would divide the mass by the molar mass:
[
\text{Number of moles} = \frac{\text{Mass (g)}}{\text{Molar mass (g/mol)}}
]
In this case:
[
\text{Number of moles} = \frac{10 \, \text{g}}{166.0 \, \text{g/mol}} \approx 0.0602 \, \text{mol}
]
Practical Applications:
Potassium iodide is used in medical treatments for thyroid protection during radiation exposure and as a reagent in chemical reactions. Understanding its molar mass is essential for preparing accurate solutions and dosages.