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# $\text{HN}{{\text{O}}_{3}}$ used as a reagent has specific gravity of 1.42 g/mL and contains 70% by strength $\text{HN}{{\text{O}}_{3}}$. Calculate the value of 100x if x mL is the volume of acid that contains 63 g pure acid:A. 63.38B. 63.00C. 63.20D. None of these

Hint: This question is based on density and percentage by strength of $\text{HN}{{\text{O}}_{3}}$. Use a unitary method to find the volume of acid. 1.42 g/mL means 1 mL of volume has 1.42 grams of $\text{HN}{{\text{O}}_{3}}$. 70% by strength means 70 grams of $\text{HN}{{\text{O}}_{3}}$ in 100 mL of volume.

Step (1) The density of $\text{HN}{{\text{O}}_{3}}$ solution is 1.42 g/mL means that 1 mL of volume has 1.42 grams of $\text{HN}{{\text{O}}_{3}}$ and 100 mL of volume has 70 grams of $\text{HN}{{\text{O}}_{3}}$.
So, the mass of pure $\text{HN}{{\text{O}}_{3}}$ in 100 mL of volume is $70\times 1.42$ grams or 99.4 grams.
Then, 63 grams of pure acid will be present in $\dfrac{100\times 63}{99.4}$ mL of volume which is equal to 63.38 ml.