Concentrated nitric acid used in laboratory work is \(68\%\) nitric acid by mass in aqueous solution. What should be the molarity of such a sample of the acid if the density of the solution is \(1.504\, \text{g mL}^{–1}?\)
Solution and Explanation
Concentrated nitric acid used in laboratory work is \(68\%\) nitric acid by mass in an aqueous solution.
This means that 68g of nitric acid is dissolved in 100g of the solution.
Molar mass of nitric acid \((\text{HNO}_3) = 1 \times 1 + 1 \times14 + 3 \times 16 = 63 \,\text{g mol}^{ - 1}\)
Then, number of moles of \(\text{HNO}_3 =\frac{68}{63}\, \text{mol}\)
\(=1.079\text{mol}\)
Given,
Density of solution \(= 1.504 \,\text{g mL}^{ - 1 }\)
Volume of 100g solution \(=\frac{100}{1.504} \text{mL}\)
\(=66.49\text{mL}\)
\(=66.49 \times 10-3\text{L}\)
Molarity of solution\(=\frac{1.079\,\text{mol}}{66.49 \times 10^{-3}\text{L}}\)
\(=16.3 \text{M}\)
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Concepts Used:
Concentration of Solutions
It is the amount of solute present in one liter of solution.
Concentration in Parts Per Million - The parts of a component per million parts (106) of the solution.
Mass Percentage - When the concentration is expressed as the percent of one component in the solution by mass it is called mass percentage (w/w).
Volume Percentage - Sometimes we express the concentration as a percent of one component in the solution by volume, it is then called as volume percentage
Mass by Volume Percentage - It is defined as the mass of a solute dissolved per 100mL of the solution.
Molarity - One of the most commonly used methods for expressing the concentrations is molarity. It is the number of moles of solute dissolved in one litre of a solution.
Molality - Molality represents the concentration regarding moles of solute and the mass of solvent.
Normality - It is the number of gram equivalents of solute present in one liter of the solution and it is denoted by N.
Formality - It is the number of gram formula present in one litre of solution.