Ethylene glycol, C2H6O2, is the principal constituent of auto-mobile antifreeze. If the density of a 40.0 mass % solution of ethylene glycol in water is 1.0514 g/mL at 20 °C, what is the molarity?

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 units of moles per liter (mol/L). To calculate molarity, one must know the amount of solute in moles and the total volume of the solution in liters. This concept is crucial for understanding how concentrated a solution is and for performing stoichiometric calculations in chemical reactions.

Density

Density is defined as mass 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 solution helps determine the total volume of the solution when the mass of the solution is known. Understanding density is essential for converting between mass and volume, which is necessary for calculating molarity.

Mass Percent Concentration

Mass percent concentration is a way to express the concentration of a solution, calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100. In this case, a 40.0 mass % solution of ethylene glycol means that 40 grams of ethylene glycol are present in every 100 grams of the solution. This concept is important for determining the amount of solute in a given mass of solution, which is a key step in calculating molarity.