Chemistry - Concentration Terms Question with Solution | TestHub
A mixture of ethanol and nitric acid, called nital, is an industrial etching agent. A student prepared a 20.0 mL solution of nital using 0.70 mL of aqueous nitric acid solution of unknown concentration and 19.3 mL of 98% ethanol. The student determined by titration that the final concentration of nitric acid in the nital etching agent was by mass. The density of ethanol was and the density of the unknown concentration of aqueous was . What was the original concentration of , in , in the 0.70 mL reagent the student used for the nital solution preparation?
Answer:
Solution:
Final nital solution volume
It is made from:
0.70 mL of aqueous HNO₃ (density 1.4 g mL⁻¹)
19.3 mL of 98% ethanol (density 0.8 g mL⁻¹)
Final nitric acid concentration in nital = 4.0% by mass
Mass of aqueous HNO₃ solution:
Mass of ethanol solution:
Total mass of nital (assuming volumes are additive and no mass loss):
The final mixture is 4.0% by mass HNO₃.
This pure HNO₃ came entirely from the 0.98 g of the unknown aqueous solution.
Therefore, the original nitric acid reagent was 67% w/w HNO₃.