Question

How many grams of concentrated nitric acid solution should be used to prepare 250 mL of 2.0 M HNO₃? The concentrated acid is 70% HNO₃.

• A. 45.0 g conc. HNO₃
• B. 90.0 g conc. HNO₃
• C. 70.0 g conc. HNO₃
• D. 54.0 g conc. HNO₃

Answer 1

The Correct Option is A

To determine how many grams of concentrated nitric acid solution are required to prepare 250 mL of 2.0 M HNO₃, we follow these steps:

1. 2.0 \, \text{M} = \frac{2.0 \, \text{moles of} \, \text{HNO}_{3}}{1 \, \text{L solution}}

   This means each liter of the solution contains 2 moles of HNO₃.

2. First, calculate the moles of HNO₃ in 250 mL:

   Since 1 L = 1000 mL, convert the volume of the solution to liters:

   Volume in liters = \frac{250 \, \text{mL}}{1000 \, \text{mL/L}} = 0.25 \, \text{L}

   The number of moles required in 0.25 L = 0.25 \, \text{L} \times 2.0 \, \text{M} = 0.5 \, \text{moles of HNO}_{3}

3. The molecular weight of HNO₃ is approximately 63 g/mol.

   Thus, the mass of HNO₃ needed = 0.5 \, \text{moles} \times 63 \, \text{g/mol} = 31.5 \, \text{g}

4. The concentrated nitric acid is 70% HNO₃ by weight.

   If x grams of the concentrated solution is needed, then:

   0.70x = 31.5 \, \text{g}

   Solve for x:

   x = \frac{31.5 \, \text{g}}{0.70} = 45.0 \, \text{g}

5. Therefore, you need 45.0 g of concentrated nitric acid solution to prepare 250 mL of 2.0 M HNO₃.

Conclusion: The correct answer is 45.0 \, \text{g Con. HNO}_{3}, which matches with the provided correct option.