Molarity Calculator
Molarity is how many moles of a dissolved substance are in each litre of solution. Enter the mass of the solid, its molar mass and the total volume.
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How it works
Moles are the mass in grams divided by the molar mass, which is the mass of one mole of the substance. Molarity is the moles divided by the volume in litres.
Molar mass is listed for each substance on a periodic table or a chemical data sheet. Use the total volume of the finished solution, not just the water you started with.
Worked example
Dissolving 0.2 oz of a solid with a molar mass of 58.44 in 2 cup gives 0.097 moles, and a molarity of 0.205 moles per litre.
Questions
What is a mole?
A mole is a counting unit for atoms or molecules, about 6.022 times 10 to the 23rd power of them. It lets chemists count by mass.
Why use the final volume?
A dissolved solid takes up some space in the liquid, so the finished volume is the right one to divide by.
Can I use it for a gas?
Not directly. Gases are usually measured by volume at a set temperature and pressure, which this does not handle.
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