Skip to main content
Pearson+ LogoPearson+ Logo
Ch.13 - Properties of Solutions
All textbooksBrown 14th EditionCh.13 - Properties of SolutionsProblem 49a
Previous problem
Next problem
Chapter 13, Problem 49a

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?

Verified Solution

Video duration:
4m
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mole Fraction

Mole fraction is a way of expressing the concentration of a component in a mixture. It is defined as the ratio of the number of moles of a specific component to the total number of moles of all components in the solution. This concept is crucial for calculating the mole fraction of methanol in the solution, as it allows us to quantify the relative amount of methanol compared to acetonitrile.
Recommended video:
Guided course
00:36
Mole Fraction Formula

Density and Volume Relationship

Density is defined as mass per unit volume and is a key property of substances. In this problem, the densities of acetonitrile and methanol are provided, which allows us to convert their volumes into masses. Understanding how to use density to find mass is essential for determining the number of moles of each component, which is necessary for calculating the mole fraction.
Recommended video:
Guided course
01:09
Relationship of Volume and Moles Example

Calculating Moles from Mass

To find the number of moles of a substance, one can use the formula: moles = mass (g) / molar mass (g/mol). This concept is important in this question because, after determining the masses of methanol and acetonitrile from their respective volumes and densities, we need to convert these masses into moles to compute the mole fraction of methanol in the solution.
Recommended video:
Guided course
03:12
Molar Mass Calculation Example
Previous problem
Next problem
Related Practice
Textbook Question
Suppose that one wishes to use reverse osmosis to reduce the salt content of brackish water containing 0.22 M total salt concentration to a value of 0.01 M, thus render- ing it usable for human consumption. What is the mini- mum pressure that needs to be applied in the permeators (Figure 18.20) to achieve this goal, assuming that the oper- ation occurs at 298 K? (Hint: Refer to Section 13.5.)
544
views
Textbook Question

Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 80.5 g of ascorbic acid dissolved in 210 g of water has a density of 1.22 g/mL at 55 °C. Calculate (a) the mass percentage,

531
views
Textbook Question

Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 80.5 g of ascorbic acid dissolved in 210 g of water has a density of 1.22 g/mL at 55 °C. Calculate (c) the molality,

565
views
Textbook Question

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?

1014
views
Textbook Question

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?

1153
views
Textbook Question

The density of toluene (C7H8) is 0.867 g/mL, and the density of thiophene (C4H4S) is 1.065 g/mL. A solution is made by dissolving 8.10 g of thiophene in 250.0 mL of toluene. (a) Calculate the mole fraction of thiophene in the solution.

592
views