Question

Hydrogen cyanide, HCN, is a poisonous gas. The lethal dose is approximately 300. mg HCN per kilogram of air when inhaled. The density of air at 26 ∘C is 0.00118 g/cm3. Consider the formation of HCN by the reaction of NaCN (sodium cyanide) with an acid such as H2SO4 (sulfuric acid):

2NaCN(s)+H2SO4(aq)→Na2SO4(aq)+2HCN(g)

What mass of NaCN gives the lethal dose in the room? partc:

HCN forms when synthetic fibers containing Orlon^® or Acrilan^® burn. Acrilan^® has an empirical formula of CH2CHCN, so HCN is 50.9%of the formula by mass. A rug in the laboratory measures 12.0× 14.0 ft and contains 30.0 oz of Acrilan^® fibers per square yard of carpet. If the rug burns, what mass of HCN will be generated in the room? Assume that the yield of HCN from the fibers is 20.0% and that the carpet is 39.0 % consumed.

Answer 1

1) Moles of lethal dose of HCN per kg of air=3.00*10^-3 g/molar mass=3.00*10^-3 g/27g/mol=0.11*10^-3 moles

From the balanced reaction we see that,

2 moles NaCN is produced by 2 moles HCN

So 1 moles NaCN is produced by 1 moles HCN

Or, 0.11*10^-3 moles of HCN =lethal dose of HCN is produced by 0.11*10^-3 moles of NaCN

Mass of NaCN that gives lethal dose=.0.11*10^-3 moles of NaCN* it’s molar mass=0.11*10^-3 moles of NaCN*49 g/mol=0.00539 g/kg of air

2) Area of rug=12.0*14.0 ft =168.0 sq ft

[1yrd = 3 ft

1 sq yrd=3^2 ft2=9sq ft]

1 oz=28.35 g]

Given,

Mass of acrilan per sq yrd (per 9 sq ft)=30.0 oz=30.0*28.35 g/oz=850.5 g

Consequently mass of acrilan per sq ft=850.5 g/9 sq ft=94.5 g/sq ft

When burned mass of carpet consumed=39% of 168.0 sq ft=0.39*168.0 sq ft=65.52 sq ft

So, mass of acrilan burned=65.52 sq ft * 94.5 g/sq ft=6191.64 g

Mass of HCN produced =20.0% 0f 6191.64 g=0.20 *6191.64 g=1238.33 g