To calculate the molarity (M) of a solution, you need to know the amount of solute (in moles) and the volume of the solution (in liters). In this case, you are given the mass of NaCl and the volume of the solution.
- First, convert the given mass of NaCl to moles.
The molar mass of NaCl is the sum of the atomic masses of sodium (Na) and chlorine (Cl). Na: 1 atomic mass unit (amu) Cl: 35.5 amu
Molar mass of NaCl = 1(22.99 amu) + 1(35.5 amu) = 58.49 amu
To convert grams to moles, divide the given mass by the molar mass: moles of NaCl = 0.25 g / 58.49 g/mol ≈ 0.00428 mol
- Next, calculate the molarity using the formula:
Molarity (M) = moles of solute / volume of solution (in liters)
Molarity (M) = 0.00428 mol / 1.5 L = 0.00285 mol/L
Therefore, the molarity of the 1.5L solution containing 0.25g of NaCl is approximately 0.00285 mol/L or 2.85 mM (millimolar).