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AL Chem
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1. When 15 ml of a gaseous hydrocarbon H were mixed with 70 ml of oxygen (excess) and iginted inside a gratuated tube in the presence of concentrated H2SO4, vol of residual gas was 47.5 ml this was reduced to 17.5 ml by treatment with caustic potash. All vol are measured in same conditions of Temp and Pressure.... 顯示更多 1. When 15 ml of a gaseous hydrocarbon H were mixed with 70 ml of oxygen (excess) and iginted inside a gratuated tube in the presence of concentrated H2SO4, vol of residual gas was 47.5 ml this was reduced to 17.5 ml by treatment with caustic potash. All vol are measured in same conditions of Temp and Pressure. Find tje molecular formula of hydrocarbon H.
最佳解答:
1. Let CxHy be the molecular formula of the hydrocarbon. CxHy + (x+y/4)O2 → xCO2 + (y/2)H2O (All H-2O formed is absorbed by the concentrated H2SO4.) For all gases under constant T and P, volume ratio = mole ratio Volume ratio CxHy : O2 : CO2 = 1 : (x+y/4) : x Volume of CxHy used = 15 cm3 Volume of O2 used = 15(x+y/4) cm3 Volume of CO2 = 15x cm3 Consider the volume of CO2 formed: 15x = 47.5-17.5 15x = 30 x = 2 Consider the volume of O2 used: 15(x+y/4) = 70-17.5 x+y/4 = 3.5 2+y/4 = 3.5 y/4 = 1.5 y = 6 Hence, the molecular formula = C2H6 = 2008-09-29 23:57:33 補充： 1 mL = 1 cm^3
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