1) Place the following four species in order of increasing boiling point. SCl 2
ID: 477575 • Letter: 1
Question
1)
Place the following four species in order of increasing boiling point.
SCl2, CH3CH3, HCl, Ne
2)
Rationalize the observation that CH3CH2OH, ethanol has a boiling point of 78.0 °C, whereas a compound with the same empirical formula, dimethyl ether (CH3OCH3), boils at -24.9°C.
A. Ethanol has stronger intermolecular forces than dimethyl ether.
B. Dimethyl ether molecules are more symmetric than molecules of ethanol.
C. Ethanol molecules have more linear shape than molecules of dimethyl ether.
D. Dimethyl ether has stronger intermolecular forces than ethanol.
Explanation / Answer
1) boiling point of Ne = -246 oC
boiling point of CH3CH3 = -89 oC
boiling point of HCl = -85.05 oC
boiling point of SCl2 = 59.6 oC
More is the molecular weight, higher the boiling point.
Increasing order of molecular weight : Ne < CH3CH3 < HCl < SCl2
Therefore,
Increasing order of boiling point = Ne < CH3CH3 < HCl < SCl2
2) ans = A
Ethanol has stronger intermolecular force i.e. Hydrogen baonding where as dimethyl ether do not.
Hydrogen bonding is an electrostatic attraction between hydrogen atom which is attached highly electronegative atom like F,N,O of one molecule and nearby highly electronegative atom of another molecule.
Ex: H-O--H , F-H---F, N-H---N
The hydrogen atom attached to oxygen of one alcohol molecule forms hydrogen bonding with oxygen atom of another alcohol.
So, more temperature is required to seperate these two molecules thus rises the boiling point.
Therefore, alcohols have higher boiling point than ethers with the same number of carbon atoms.
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