Chapter 4

Federal regulations set an upper limit of 50 parts per million (ppm) of ${\mathrm{NH}}_3$ in the air in a work environment [that is, 50 molecules of ${\mathrm{NH}}_3(g)$ for every million molecules in the air]. Air from a manufacturing operation was drawn through a solution containing $1.00\times {10}^2\mathrm{mL}$ of $0.0105\mathrm{M}\mathrm{HCl}$. The ${\mathrm{NH}}_3$ reacts with $\mathrm{HCl}$ as follows: $${\mathrm{NH}}_3(aq)+\mathrm{HCl}(aq)⟶{\mathrm{NH}}_4\mathrm{Cl}(aq)$$ After drawing air through the acid solution for $10.0\min$ at a rate of $10.0\mathrm{L}/\min ,$ the acid was titrated. The remaining acid needed $13.1\mathrm{mL}$ of $0.0588\mathrm{M}\mathrm{NaOH}$ to reach the equivalence point. (a) How many grams of ${\mathrm{NH}}_3$ were drawn into the acid solution? (b) How many ppm of ${\mathrm{NH}}_3$ were in the air? (Air has a density of $1.20\mathrm{g}/\mathrm{L}$ and an average molar mass of $29.0\mathrm{g}/\mathrm{mol}$ under the conditions of the experiment.) (c) Is this manufacturer in compliance with regulations?