Answer: 0.24 Moles. WARNING: "mm" in the original question seems to be a typo and was assumed to be "M" (moles per liter) for concentration.
Explanation:
To calculate the number of moles of solute needed to prepare a solution, we can use the formula:
moles of solute = concentration (in moles per liter) * volume of solution (in liters)
Given:
Concentration of NaCl solution = 0.8 M (moles per liter)
Volume of solution to be prepared = 300 mL = 300/1000 L (converted to liters)
Plugging in the given values:
Concentration = 0.8 M
Volume of solution = 300/1000 L
moles of NaCl = 0.8 M * 300/1000 L
Calculating:
moles of NaCl = 0.24 moles
So, 0.24 moles of NaCl are needed to prepare 300 mL of a 0.8 M NaCl solution.