Ethylene oxide $(C_2{H}_{4}O)$ is a high volume chemical intermediate that is used to produce

glycol and polyethylene glycol. Ethylene oxide is produced by the partial oxidation of

ethylene $(C_2{H}_4)$ using a solid catalyst in a fixed bed reactor:

$2C_2{H}_4+O22C_2{H}_{4}O$

Unfortunately, a portion of the ethylene reacts completely to $C{O}_2$ and $H_{2}O$ :

$C_2{H}_4+3O_{2}2C{O}_2+2H_{2}O$

The product gas leaving a fixed bed ethylene oxide reactor has the following water free

composition: $20\mathrm{.}5\%C_2{H}_{4}O,72\mathrm{.}7\%N_2,2\mathrm{.}3\%O_2,$ and $4\mathrm{.}5\%C{O}_2.$ Determine the percent

excess air used in the reactor, based on the desired reaction $(1)$ and the mass of ethylene feed

$($in $lb\frac{s}{h}r)$ required to produce $100,000$ tons$/$year of ethylene oxide.