Finding the Mass of Nitric Acid in a Solution

In this article, we will explore the process of finding the mass of nitric acid (HNO3) in a solution using specific gravity (SG) and purity percentage. This is a common requirement in chemical industries for quality control and product specification. The given parameters for a 500 mL solution are:

Specific gravity (SG) 1.42 Purity by mass 69% Volume of solution 500 mL

Understanding Specific Gravity and Mass Calculation

Specific Gravity (SG) is a dimensionless quantity representing the ratio of the density of a substance to the density of water. Water's density is approximately 1 g/mL at room temperature. Therefore, the density of the solution can be calculated as:

Density of the solution Specific Gravity × Density of water

1.42 g/mL × 1 g/mL

1.42 g/mL

Given the volume of the solution, we can now find the mass of the solution:

Mass of solution Volume × Density

500 mL × 1.42 g/mL

710 g

Calculating the Mass of Nitric Acid

The purity of the solution is 69 by mass, meaning 69% of the solution's mass is HNO3. The mass of HNO3 present in the solution can be calculated as:

Mass of HNO3 Mass of solution × (Purity / 100)

710 g × (69 / 100)

489.9 g

Therefore, the mass of nitric acid in the solution is approximately 489.9 grams.

Calculating Molarity and Molality

To further understand the concentration of the solution, we can calculate the molarity and molality.

Molarity (M) is defined as the number of moles of solute in one liter of solution. The molar mass of HNO3 is 63.01 g/mol. First, we calculate the total mass of the solution:

Total mass of solution Density × Volume

1.42 g/mL × 500 mL

710 g

Then, the mass of HNO3 is:

Mass of HNO3 710 g × (69 / 100)

490 g

The molarity (M) is then calculated as:

Molarity (Mass of HNO3 / Molar mass of HNO3) / Volume in liters

(490 g / 63.01 g/mol) / 0.5 L

1.558 M

Similarly, the molality (m) can be calculated as the ratio of the number of moles of HNO3 to the mass of the solvent in kilograms. First, we need to find the mass of the solvent (water):

Mass of solvent (H2O) Total mass of solution - Mass of HNO3

710 g - 490 g

220 g

The molality (m) is then:

Molality (Number of moles of HNO3) / Mass of solvent (kg)

(490 g / 63.01 g/mol) / 0.220 kg

35.32 m

Conclusion

By following these steps, we can accurately determine the mass of nitric acid in a given solution. This information is crucial for various applications in the chemical industry, ensuring that the solution meets specific purity and concentration requirements. Understanding both molarity and molality provides a comprehensive overview of the solution's concentration and its behavior under different conditions.