A certain hydrocarbon, X, contains 85.7% of carbon by mass. When 10.0 cm^3 of X underwent complete combustion in 80.0 cm^3 of oxygen, the remaining gases occupied 60.0 cm^3. After shaking these gases with aqueous sodium hydroxide, the final volume of gas remaining was 20.0 cm^3. All volumes were measured at room temperature and pressure.
(Given the atomic mass of C = 12, H = 1.)
i) Calculate the empirical and molecular formula
ii)Compound X exists as a pair of cis-trans isomers.
Deduce the structural formulae of X.
organic chemistry question
2010-04-18 7:07 pm
回答 (2)
2010-04-18 8:10 pm
✔ 最佳答案
i)Mole ratio C : H = (85.7/12) : (100 - 85.7)/1 = 7.14 : 14.3 = 1 : 2
Empirical formula = CH2
Let CaHb be the molecular formula of X.
CaHb + (a + b/4)O2 → aCO2 + (b/2)H2O
Mole ratio CaHb : CO2
1 : a = 10 : (60 - 20)
a = 4
Mole ratio CaHb : O2
1 : (a + b/4) = 10 : (80 - 20)
1 : (4 + b/4) = 10 : 60
10(4 + b/4) = 60
40 + 2.5b = 60
2.5b = 20
b = 8
Molecular formula = C4H8
ii)
structural formula of X: CH3CH=CHCH3
參考: wanszeto
2010-04-18 9:21 pm
To wanszeto:
Isn't it better to let X be CaH2a??
So that you can know it is C4H8 immediately after you calculated a.....
Isn't it better to let X be CaH2a??
So that you can know it is C4H8 immediately after you calculated a.....
收錄日期: 2021-04-19 21:54:27
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