AL Chem - Ans.fyi 參考答案

AL Chem

[匿名]

2008-09-30 1:42 am

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.

回答 (1)

Uncle Michael

2008-09-30 7:31 am

✔ 最佳答案

1.
Let CxHy be the molecular formula of the hydrocarbon.

CxHy + (x+y/4)O2 → xCO2 + (y/2)H2O
(All H2O 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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