Final answer:
To calculate the moles of sodium chloride in the solution, multiply the molarity (1.20 M) by the volume in liters (0.250 L), which results in 0.30 moles, making option A the correct answer.
Step-by-step explanation:
The question asks to calculate the number of moles of sodium chloride in 250 mL of a 1.20 M sodium chloride solution. Molarity (M) is defined as the number of moles of solute per liter of solution. To find the moles of NaCl, we can use the formula: moles = molarity (M) × volume (L). Since we have 250 mL of the solution, we first need to convert milliliters to liters by dividing by 1000.
Volume in liters = 250 mL / 1000 = 0.250 L
We then multiply the molarity of the solution by the volume in liters: Moles of NaCl = 1.20 moles/L × 0.250 L = 0.30 moles.
Therefore, the correct answer is: A: 0.30 moles.