Commercial concentrated aqueous ammonia is 28% NH₃ by mass and has a density of 0.90 g/mL. What is the molarity of this solution?

Key Concepts

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (mol/L) and is crucial for understanding how much solute is present in a given volume of solution. To calculate molarity, one must know the amount of solute in moles and the total volume of the solution in liters.

Density

Density is the mass of a substance per unit volume, typically expressed in grams per milliliter (g/mL) or kilograms per cubic meter (kg/m³). In this context, the density of the ammonia solution allows us to convert the mass of the solution into volume, which is essential for calculating molarity. Understanding density helps in determining how much solution corresponds to a given mass.

Percent by Mass

Percent by mass is a way to express the concentration of a component in a mixture, calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100. In this case, the 28% by mass of NH₃ indicates that there are 28 grams of ammonia in every 100 grams of solution. This information is vital for determining the amount of solute available for molarity calculations.