"Published in Suisun City, California, USA"
A waste acid from a nitrating process contains 23% HNO3, 57% H2SO4, and 20% water by weight. This acid is to be concentrated to contain 27% HNO3, 60% H2SO4 by the addition of concentrated H2SO4 containing 93% H2SO4 and concentrated HNO3 containing 90% HNO3. Calculate the amounts in kg of waste and concentrated acids that must be combined to obtain 1,000 kg of desired mixture.
Solution:
The given word problem is about the mixing of waste and concentrated acids which involves the principles of Stoichiometry. 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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Basis: 1,000 kg of Desired Mixture
Let x = be the amount of Waste Acid
y = be the amount of Concentrated Sulfuric Acid
z = be the amount of Concentrated Nitric Acid
Overall Material Balance of Mixer:
Material Balance of H2SO4:
Material Balance of HNO3:
Substitute the values of y and z to the first equation, we have
Substitute the value of x to the second equation, we have
Substitute the value of x to the third equation, we have
Therefore,
Amount of Waste Acid = 418.618 kg
Amount of Conc. Sulfuric Acid = 388.548 kg
Amount of Conc. Nitric Acid = 192.834 kg