To find the molarity of a solution, you can use the formula:
\[ \text{Molarity (M)} = \frac{\text{moles of solute}}{\text{liters of solution}} \]
First, you need to calculate the number of moles of KF (potassium fluoride). The molar mass of KF can be calculated from the atomic masses of potassium (K) and fluoride (F):
- Potassium (K) has an atomic mass of approximately 39.1 g/mol.
- Fluoride (F) has an atomic mass of approximately 19.0 g/mol.
Now, calculate the molar mass of KF:
\[ \text{Molar mass of KF} = 39.1 , \text{g/mol} + 19.0 , \text{g/mol} = 58.1 , \text{g/mol} \]
Next, calculate the number of moles of KF in 58.0 g:
\[ \text{moles of KF} = \frac{58.0 , \text{g}}{58.1 , \text{g/mol}} \approx 0.997 , \text{moles} \]
Now, with the number of moles calculated, we can find the molarity:
\[ \text{Molarity (M)} = \frac{0.997 , \text{moles}}{4.0 , \text{L}} \approx 0.249 , \text{M} \]
Therefore, the molarity of the solution is approximately 0.249 M.