Phosgene (CCl, O) is a colorless gas that was used as an agent of chemical
warfare in World War I. It has the odor of new-mown hay (which is a good
warning if you know the smell of new-mown hay). Pete Brouillette, an
innovative chemical engincering student, came up with what he believed was an
effective new process that utilized phosgene as a starting material. He
immediately set up a reactor and a system for analyzing the reaction mixture
with a gas chromatograph. To calibrate the chromatograph (i.e., to determine
its response to a known quantity of phosgene), he evacuated a 15.0 cm length
of tubing with an outside diameter of \(0.635 \mathrm{cm}\) and a wall thickness
of \(0.559 \mathrm{mm}\), and then connected the tube to the outlet valve of a
cylinder containing pure phosgene. The idea was to crack the valve, fill the
tube with phosgene, close the valve, feed the tube contents into the
chromatograph, and observe the instrument response.
What Pete hadn't thought about (among other things) was that the phosgene was
stored in the cylinder at a pressure high enough for it to be a liquid. When
he opened the cylinder valve, the liquid rapidly flowed into the tube and
filled it. Now he was stuck with a tube full of liquid phosgene at a pressure
the tube was not designed to support. Within a minute he was reminded of a
tractor ride his father had once given him through a hayfield, and he knew
that the phosgene was leaking. He quickly ran out of the lab, called campus
security, and told them that a toxic leak had occurred, that the building had
to be evacuated, and the tube removed and disposed of properly. Personnel in
air masks shortly appeared, took care of the problem, and then began an
investigation that is still continuing.
(a) Show why one of the reasons phosgene was an effective weapon is that it
would collect in low spots soldiers often mistakenly entered for protection.
(b) Pete's intention was to let the tube equilibrate at room temperature (
\(23^{\circ} \mathrm{C}\) ) and atmospheric pressure. How many gram-moles of
phosgene would have been contained in the sample fed to the chromatograph if
his plan had worked?
(c) The laboratory in which Pete was working had a volume of \(2200
\mathrm{ft}^{3}\), the specific gravity of liquid phosgene is \(1.37,\) and Pete
had read somewhere that the maximum "safe" concentration of phosgene in air is
\(0.1 \mathrm{ppm}\) \(\left(0.1 \times 10^{-6} \mathrm{mol} \mathrm{CCl}_{2}
\mathrm{O} / \mathrm{mol}\) air) \right. Would the "safe" concentration have
been exceeded if all the liquid phosgene in the tube had evaporated into the
room? Even if the limit would not have been exceeded, give several reasons why
the lab would still have been unsafe.
(d) List several things Pete did (or failed to do) that made his experiment
unnecessarily hazardous.
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