What This Calculator Does
This tool calculates the number of moles of a dissolved substance (the solute) when you know the solution's molarity and its volume. It applies the fundamental relationship \(n = M \times V\), where n is the amount of substance in moles, M is the molar concentration in moles per liter (mol/L, also written as molar or M), and V is the volume in liters. This is one of the most frequently used equations in general and analytical chemistry.
How to Use It
Enter the molarity of your solution in mol/L and the volume in liters, then read the result in moles. The calculator also converts the answer to millimoles for convenience when working with small quantities. If your volume is given in milliliters, divide by 1000 first (for example, 250 mL = 0.25 L).
The Formula Explained
Molarity is defined as moles of solute divided by liters of solution: \(M = n / V\). Rearranging to solve for the amount of substance gives the following:
$$n = M \times V$$
Because molarity already carries units of mol/L, multiplying by a volume in liters cancels the liters and leaves a result in moles.
Worked Example
Suppose you have 2 liters of a 0.5 mol/L sodium chloride solution. The moles of NaCl present are:
$$n = 0.5 \text{ mol/L} \times 2 \text{ L} = 1 \text{ mol}$$
That equals 1000 millimoles. If instead you had 250 mL (0.25 L) of the same solution, you would have \(0.5 \times 0.25 = 0.125\) mol, or 125 mmol.
FAQ
What units should the volume be in? Liters. Convert milliliters to liters by dividing by 1000.
Does this give grams? No — it gives moles. To convert moles to grams, multiply by the substance's molar mass (g/mol).
What is molarity? Molarity (M) is the number of moles of solute per liter of solution, a measure of concentration.
