How many grams of KNO3 are required to prepare 250. mL of a 0.135 M solution?

• A. 1.70 g
• B. 0.90 g
• C. 3.41 g
• D. 5.10 g

Answer: (C)

Verified step by step guidance

1. Identify the given information: volume of solution (V) = 250. mL, molarity (M) = 0.135 M, and the solute is KNO\_3.
2. Convert the volume from milliliters to liters because molarity is expressed in moles per liter: \(V(\text{L}) = \frac{250.\ \text{mL}}{1000}\).
3. Use the molarity definition to find the number of moles of KNO\_3 needed: \(\text{moles} = M \times V(\text{L})\).
4. Calculate the molar mass of KNO\_3 by adding the atomic masses of K, N, and O (potassium, nitrogen, and oxygen respectively).
5. Convert moles of KNO\_3 to grams using the molar mass: \(\text{mass} = \text{moles} \times \text{molar mass}\).