How to Prepare 3M NH3 from Concentrated Ammonia: A Step-by-Step Guide

Understanding the process of preparing specific concentrations of ammonia is crucial for students and professionals in the field of chemistry. This article will guide you through the detailed steps to prepare 3 moles per liter (3 M) of ammonia (NH3) from a 28.4 percent ammonium by weight concentrated ammonia solution with a density of 0.808 grams per milliliter (g/mL). By the end of this guide, you will have a clear understanding of the calculations and methods involved in this preparation.

Keywords: ammonia concentration, molarity calculation, chemical preparation

Understanding Ammonia Concentration and Molarity

Ammonia, NH3, is a colorless, pungent gas that is often used in laboratory and industrial settings. The concentration of ammonia can be expressed in various ways, such as mass percent, molarity, or normality. In this context, we will focus on the concentration of ammonia as a mass percentage and the molarity of a solution.

Mass Percentage of Ammonia

The original solution is stated to have a mass percentage of 28.4 percent ammonia by weight. This means that in 100 grams of the solution, there are 28.4 grams of ammonia. This information is crucial for determining the amount of ammonia present in a given volume of the concentrated solution.

Molarity Calculation

Molarity (M) is the number of moles of solute per liter of solution. The key information needed for this calculation includes the molecular weight of ammonia and the density of the concentrated solution.

Step 1: Calculate the Mass of Ammonia in 100 ml of Solution

Given that the density of the concentrated ammonia solution is 0.808 g/mL, the mass of 100 mL of the solution can be calculated as:

Mass of 100 mL solution 100 mL × 0.808 g/mL 80.8 grams

The mass of ammonia in this solution can be determined from its mass percentage:

Mass of ammonia 28.4% of 80.8 grams 0.284 × 80.8 grams 22.9 grams

Step 2: Calculate the Moles of Ammonia

The molar mass of ammonia (NH3) is 17 grams per mole (g/mol). Using this information, we can calculate the number of moles of ammonia present:

Moles of ammonia Mass of ammonia / Molar mass 22.9 grams / 17 g/mol 1.35 moles

Step 3: Determine the Volume for 3 M NH3 Solution

3 M NH3 means 3 moles of ammonia per liter of solution. To find out how much of the concentrated solution is needed to prepare 3 M NH3, we use the following calculation:

Volume of 3 M NH3 Moles of ammonia / Concentration 1.35 moles / 3 moles/L 0.45 L 450 mL

Verification and Practical Considerations

It is always advisable to double-check calculations, particularly when working with potentially hazardous chemicals like ammonia. Ensure that your calculations are accurate and that the equipment you are using is clean and properly calibrated.

In a laboratory setting, it is critical to follow safety guidelines when handling concentrated ammonia solutions. Protective gear, such as gloves, goggles, and lab coats, should be worn. Ammonia solutions can be corrosive and may cause severe skin and eye irritation.

For educational purposes or small-scale experiments, it is recommended to use a glass dropper pipette to transfer the solution. Larger scale preparations may require a syringe or a peristaltic pump for precise volume control.

Conclusion

By following the detailed steps outlined in this guide, you can prepare 3 M NH3 solution from a concentrated ammonia solution with a density of 0.808 g/mL and a mass percentage of 28.4%. Understanding and accurately performing such calculations is essential in both educational and professional chemistry settings. Always prioritize safety when working with chemicals.

Keywords: ammonia concentration, molarity calculation, chemical preparation