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Ch.13 - Properties of Solutions
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.13 - Properties of SolutionsProblema 49c
Capitolo 13, Problema 49c

The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (c) Assuming that the volumes are additive, what is the molarity of CH3OH in the solution?

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Calculate the mass of methanol (CH₃OH) using its volume and density: \( \text{mass} = \text{volume} \times \text{density} \).
Determine the number of moles of methanol using its molar mass: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).
Calculate the total volume of the solution by adding the volumes of methanol and acetonitrile: \( \text{total volume} = \text{volume of CH}_3\text{OH} + \text{volume of CH}_3\text{CN} \).
Convert the total volume from mL to L, as molarity is expressed in moles per liter.
Calculate the molarity of methanol in the solution using the formula: \( \text{Molarity} = \frac{\text{moles of CH}_3\text{OH}}{\text{total volume in L}} \).

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Density

Density is defined as mass per unit volume and is typically expressed in grams per milliliter (g/mL) for liquids. It is a crucial property that helps determine how much mass of a substance is present in a given volume. In this question, the densities of acetonitrile and methanol are provided, which will be used to calculate the mass of each component in the solution.
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Density Concepts

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution (mol/L). It is an important concept in chemistry for quantifying the amount of a substance in a solution. To find the molarity of methanol in the solution, one must first calculate the number of moles of methanol and then divide by the total volume of the solution in liters.
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Molarity

Additivity of Volumes

The assumption of volume additivity states that when two liquids are mixed, the total volume of the resulting solution is the sum of the individual volumes of the liquids. This simplification is often used in calculations involving solutions, although it may not always hold true due to interactions between different substances. In this question, the total volume of the solution is calculated by adding the volumes of methanol and acetonitrile.
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Addition Reactions
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The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (b) What is the molality of the solution?

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The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (a) What is the mole fraction of methanol in the solution?

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