Chemistry Calculator

Divide the mass in grams by the molar mass to get moles, then divide by the solution volume in liters. For example, dissolving 58.44 g of NaCl (molar mass 58.44 g/mol) in 1 liter of water gives a 1.0 M solution. A 0.5 M solution of the same salt needs only 29.22 g per liter.

Multiply the initial concentration by the initial volume to get the product, then divide by the desired final concentration to find the required final volume. To dilute a 6 M HCl stock to 0.1 M, you need 0.1/6 = 0.0167 liters of stock per liter of final solution - about 16.7 mL of acid added to water to reach 1 liter total.

At standard temperature and pressure (0 degrees C and 1 atm), one mole of an ideal gas occupies 22.414 liters. Under the newer IUPAC definition using 25 degrees C and 1 bar, the molar volume is 24.79 liters. Real gases deviate slightly - CO2 at STP occupies about 22.26 liters per mole due to intermolecular attractions.

Take the negative base-10 logarithm of the hydrogen ion concentration in mol/L. A concentration of 0.001 M (10 to the minus 3) gives pH 3. Pure water at 25 degrees C has a hydrogen ion concentration of 10 to the minus 7, giving pH 7. Each pH unit represents a tenfold change in acidity.

Molarity (M) is moles of solute per liter of solution, while molality (m) is moles of solute per kilogram of solvent. For dilute aqueous solutions the values are nearly identical because 1 liter of water weighs about 1 kg. The difference matters at high concentrations or with non-aqueous solvents - a 5 M sulfuric acid solution has a molality of roughly 6.9 m because the dense solution packs more solute per liter than per kilogram of water.