What is the molality of the 40.0 mass % ethylene glycol 1C2H6O22 solution used for automobile antifreeze?

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Determine the mass of the solution. Assume you have 100 grams of solution for simplicity. This means you have 40 grams of ethylene glycol and 60 grams of water.

Convert the mass of water from grams to kilograms to use in the molality calculation. Since 1000 grams are in a kilogram, divide the mass of the water by 1000.

Calculate the molar mass of ethylene glycol (C2H6O2). The molar mass is calculated by adding the atomic masses of each element in the compound: C (12.01 g/mol) imes 2 + H (1.008 g/mol) imes 6 + O (16.00 g/mol) imes 2.

Determine the number of moles of ethylene glycol by dividing the mass of ethylene glycol by its molar mass.

Calculate the molality of the solution using the formula: molality = moles of solute / kilograms of solvent.

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주요 개념

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Molality

Molality is a measure of the concentration of a solute in a solution, defined as the number of moles of solute per kilogram of solvent. It is particularly useful in situations where temperature changes may affect volume, as it relies on mass rather than volume. The formula for calculating molality (m) is m = moles of solute / mass of solvent (kg).

Mass Percent

Mass percent is a way of expressing the concentration of a component in a mixture, calculated as the mass of the component divided by the total mass of the mixture, multiplied by 100. In this case, a 40.0 mass % ethylene glycol solution means that there are 40 grams of ethylene glycol in every 100 grams of the solution. Understanding mass percent is crucial for converting to moles and determining the amount of solvent.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For ethylene glycol (C2H6O2), the molar mass is approximately 62.07 g/mol. Knowing the molar mass is essential for converting between grams and moles, which is necessary for calculating molality from mass percent.