Understanding Mole Fraction Calculation in Solutions

Calculating the mole fraction of a solution is an essential skill in chemistry, particularly when dealing with solute and solvent mixtures. This article will guide you through the process of determining the mole fraction in two different solutions: one containing sucrose and water, and another consisting of a 30% NaOH solution by mass. We will also explore the general procedure to calculate mole fraction and ensure our answers are accurate according to Google's SEO standards.

Mole Fraction Calculation for 100g Sucrose in 100g Water

To understand the mole fraction calculation for a 100g sucrose solution with 100g water, let's break down the process step-by-step.

Step-by-Step Calculation

The molar mass of sucrose (C12H22O11) is calculated as follows:

12 × 12 (C atoms) 22 × 1 (H atoms) 11 × 16 (O atoms) 342 g/mol

And the molar mass of water (H2O) is:

1 × 2 (H atoms) 16 (O atom) 18 g/mol

Now, let's determine the number of moles:

No. of moles of sucrose 100 g / 342 g/mol 0.292 mol

No. of moles of water 100 g / 18 g/mol 5.556 mol

The mole fraction of sucrose is then calculated as:

Mole fraction of sucrose 0.292 / (0.292 5.556) 0.050

Mole Fraction Calculation for 30% NaOH by Mass Solution

General Procedure

The general procedure for calculating mole fraction involves converting all measurements, including the solvent (usually water), to moles. Then, divide the moles of the solute of interest by the total number of moles in the solution.

Step-by-Step Calculation for 30% NaOH Solution

The molar mass of NaOH (sodium hydroxide) is:

23 (Na atom) 17 (O atom) 1 (H atom) 40 g/mol

The solution contains 100g of 30% NaOH by mass. This means that 30g of NaOH is dissolved in 70g of water.

No. of moles of NaOH (30 g / 40 g/mol) 0.75 mol

No. of moles of H2O (70 g / 18 g/mol) ≈ 3.89 mol

The mole fraction of NaOH is then calculated as:

Mole fraction of NaOH 0.75 / (0.75 3.89) 0.16

General Guidelines for Mole Fraction Calculation

To ensure accuracy in your mole fraction calculations, follow these guidelines:

Convert all substance masses to moles using their respective molar masses. Divide the moles of the solute by the total moles of all substances in the solution. Do not convert the mole fraction to a percentage. Your answer should always be between 0 and 1.

Conclusion

Calculating the mole fraction is a fundamental concept in understanding solution composition. Whether you are working with sucrose and water or sodium hydroxide and water, the process remains the same: convert all relevant masses to moles and divide the moles of interest by the total moles. This article has provided clear, concise steps to guide you through these calculations. By following these guidelines, you can accurately determine the mole fraction of any solution.

Further Reading

To dive deeper into the topic, explore resources on:
- Stoichiometry and Chemical Reactions
- Solution Concentration Calculations
- Understanding Molar Mass and Its Applications