60cm^3 of oxygen were added to 10cm^3 of a gaseous hydrocarbon. After explosion and cooling, the gases occupied 50cm^3, and after absorption by concentrated sodium hydroxide solution, 30cm^3 of oxygen remained. What would be the molecular formula of the hydorcarbon?
A. CH4
B. C2H4
C. C2H6
D. C3H6
Ans: B. Why?
F5 Chem molar volume of g
2011-04-23 2:40 am
回答 (1)
2011-04-23 7:13 am
✔ 最佳答案
Let CxHy be the molecular formula of the hydrocarbonCxHy(g) + (x + y/4)O2(g) ---> xCO2(g) + (y/2)H2O(l)
Volume of CO2 absorbed = 50 - 30 = 20 cm^3
Volume of O2 reacted = 60 - 30 = 30 cm^3
Volume ratio between CxHy : CO2 = 1 : x = 10 : 20
Thus, x = 2
Volume ratio between O2 : CO2 = x + y/4 : x = 30 : 20
(x + y/4)/x = 30/20
(2 + y/4)/2 = 3/2
y = 4
So molecular molecular of the required hydrocarbon: C2H4 (B)
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