How many grams of concentrated nitric acid solution should be used to prepare 250 mL of 2.0 M \( \text{HNO}_3 \)? The concentrated acid is 70% \( \text{HNO}_3 \).
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To prepare a diluted solution from a concentrated one, use the dilution equation \( C_1 V_1 = C_2 V_2 \).
Step 1: Use the dilution equation.
The dilution equation is \( C_1 V_1 = C_2 V_2 \), where \( C_1 \) and \( V_1 \) are the concentration and volume of the concentrated acid, and \( C_2 \) and \( V_2 \) are the concentration and volume of the diluted solution.
Step 2: Calculate the amount of concentrated acid.
The volume of the concentrated acid required is calculated as follows:
\[
\text{Mass of conc. acid} = \frac{C_2 V_2}{\text{percentage concentration}} \times 100
\]
\[
\boxed{45.0 \, \text{g}}
\]