What is the required concentration (in percent by mass) for an aqueous ethylene glycol (C2H6O2) solution to have a boiling point of 104.0 °C?

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780134112831

Guida verificata passo dopo passo

insert step 1: Understand that the boiling point elevation formula is \( \Delta T_b = i \cdot K_b \cdot m \), where \( \Delta T_b \) is the boiling point elevation, \( i \) is the van't Hoff factor, \( K_b \) is the ebullioscopic constant of the solvent, and \( m \) is the molality of the solution.

insert step 2: Calculate \( \Delta T_b \) by subtracting the normal boiling point of water (100.0 °C) from the given boiling point (104.0 °C).

insert step 3: Use the van't Hoff factor \( i = 1 \) for ethylene glycol, as it does not dissociate in solution.

insert step 4: Rearrange the boiling point elevation formula to solve for molality \( m \): \( m = \frac{\Delta T_b}{i \cdot K_b} \). Use the known \( K_b \) value for water, which is 0.512 °C kg/mol.

insert step 5: Convert the molality to percent by mass. Assume a certain mass of water (e.g., 1 kg) to find the mass of ethylene glycol using its molality, then calculate the percent by mass using the formula: \( \text{percent by mass} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100\%.\)

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Boiling Point Elevation

Boiling point elevation is a colligative property that describes how the boiling point of a solvent increases when a solute is added. This phenomenon occurs because the presence of solute particles disrupts the formation of vapor above the liquid, requiring a higher temperature to reach the boiling point. The relationship is quantified by the formula ΔT_b = i * K_b * m, where ΔT_b is the boiling point elevation, i is the van 't Hoff factor, K_b is the ebullioscopic constant, and m is the molality of the solution.

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Boiling Point Elevation

Percent by Mass Concentration

Percent by mass concentration is a way to express the concentration of a solution, defined as the mass of solute divided by the total mass of the solution, multiplied by 100. This measurement is useful for understanding how much solute is present in a given mass of solution, which is essential for calculations involving colligative properties like boiling point elevation. For example, a 10% by mass solution of ethylene glycol means that there are 10 grams of ethylene glycol in every 100 grams of solution.

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Mass Percent Calculation

Ethylene Glycol Properties

Ethylene glycol (C2H6O2) is a colorless, odorless liquid commonly used as an antifreeze and coolant. It has a relatively high boiling point compared to water, which allows it to be effective in raising the boiling point of aqueous solutions. Understanding the physical properties of ethylene glycol, including its boiling point and how it interacts with water, is crucial for calculating the required concentration to achieve a specific boiling point in a solution.

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Physical Properties

Pratica correlata

Domanda del libro di testo

Pick an appropriate solvent from Table 13.3 to dissolve each substance. State the kind of intermolecular forces that would occur between the solute and solvent in each case. a. motor oil (nonpolar) b. ethanol (polar, contains an OH group) c. lard (nonpolar) d. potassium chloride (ionic)

Domanda del libro di testo

Pick an appropriate solvent from Table 13.3 to dissolve each substance. State the kind of intermolecular forces that would occur between the solute and solvent in each case. a. isopropyl alcohol (polar, contains an OH group) c. vegetable oil (nonpolar) d. sodium nitrate (ionic)