Which statement is true about an aqueous solution that is 15.0 percent HNO3 by mass?

• A. There are 15.0 g of HNO3 in every 100 g of solution.
• B. There are 15.0 g of HNO3 in every 100 g of water.
• C. The solution is 15.0 percent HNO3 by volume.
• D. The solution contains 15.0 moles of HNO3 per liter.

Answer: (A)

Verified step by step guidance

1. Understand that percent by mass (mass percent) means the mass of solute divided by the total mass of the solution, multiplied by 100%. It is expressed as: \(\text{mass \%} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100\%\).
2. Given the solution is 15.0% HNO3 by mass, this means that in every 100 grams of the entire solution, 15.0 grams is HNO3 and the rest is water or other components.
3. Recognize that this percentage does NOT mean 15.0 grams of HNO3 per 100 grams of water, because the denominator in the percent by mass is the total solution mass, not just the solvent mass.
4. Note that percent by mass is not related to volume, so the statement about 15.0% by volume is incorrect unless volume data is given and calculated separately.
5. Also, percent by mass does not directly give moles per liter (molarity) without knowing the density of the solution to convert mass to volume and then calculating moles from mass using molar mass.