"Published in Newark, California, USA"
It is desired to have a mixed acid containing 10% HNO3, 43% H2SO4, and 17% H2O by weight. Sulfuric acid of 98% by weight is readily available. Calculate
(a) the strength of nitric acid, and
(b) the weight ratio of sulfuric acid to nitric acid.
Solution:
The given word problem is about the mixing of nitric acid and sulfuric acid which involves the principles of Stoichiometry. The strength or concentration of nitric acid is unknown and we need to solve it as well as the weight ratio of nitric acid and sulfuric acid. The total amount of a substance in the reactants or incoming ingredients must be equal to the total amount of a substance in the final products. In short, the Law of Conservation of Mass must be followed all the time. Since all incoming substances are acids, then there's no chemical reactions involved in the mixture. To illustrate the given problem, it is better to draw the flow diagram as follows
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| Photo by Math Principles in Everyday Life |
Since the weight of concentrated sulfuric acid, concentrated nitric acid, and mixed acid are not given in the problem, let's assign a basis of 100 kg of mixed acid in the problem.
Basis: 100 kg of Mixed Acid
Let x = be the amount of concentrated sulfuric acid
y = be the amount of concentrated nitric acid
Overall Material Balance of Mixer:
Material Balance of H2SO4:
Substitute the value of x to the first equation, we have
The value of y which is the amount of the concentrated nitric acid is not a pure nitric acid. We need first to get the amount of pure nitric acid in order to get the strength or concentration of concentrated nitric acid.
Material Balance of HNO3:
Therefore, the strength or concentration of concentrated nitric acid is
The weight ratio of conc. H2SO4 to conc. HNO3 is
