Tag: physical properties of alcohols and phenols

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Questions Related to physical properties of alcohols and phenols

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Alcohols of low molecular weight are:

  1. soluble in water

  2. soluble in water on heating

  3. insoluble in water

  4. insoluble in all solvents.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Alcohols of low molecular weight are soluble in water while that of high molecular weight are insoluble in water .because of high hydrogen bonding in low molecular weight Alcinous.

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Which of the following statements is not correctly showing the trend of the properties mentioned ?

  1. $CH _3CH _2OH > CH _3CH _2CH _2OH > \underset {(Solubility)}{CH _3CH _2CH _2CH _2OH}$
  2. $CH _3CH _2OH > CH _3CH _2CH _2OH > \underset {(Boiling point)}{CH _3CH _2CH _2CH _2OH}$
  3. $CH _3CH _2CH _2OH > CH _3{\underset{CH _3}{\underset{|}{CH}}}-CH _2OH >\underset{Boiling \, point}{CH _3-\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}C}}}-OH}$
  4. $CH _3-{\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}{C}}}}}-OH$<$CH _3{\underset{CH _3}{\underset{|}{CH}}}-CH _2OH$ <$CH _3CH _2CH _CH _2OH$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Boiling point and solubility of alcohols is determined by the ease and extent of H-bonding among the alcohol molecules. More is the hydrogen bonding higher is the boiling point and solubility in water. Thus, tertiary alcohols being highly hindered will have least hydrogen bonding and thus low boiling point/solubility as compared to less hindered secondary alcohol.
Therefore the order of boiling point is primary alcohol>secondary alcohol>tertiary alcohol as:
$CH _3CH _2CH _2OH>CH _3CH(CH _3)CH _2OH>CH _3C(CH _3) _2OH$
In case of linear versus branched alcohol, linear alcohol has higher melting/boiling points due to better stacking and surface area contact.
But in case of highly branched vs. branched molecules more sphere-like structure of the molecule better is the stacking thus higher will be the melting point. Thus order of melting point will be
$CH _3CH(CH _3)CH _2OH<CH _3C(CH _3) _2OH<CH _3CH _2CH _2CH _2OH$
A and B. Solubility and boiling point of alcohols depends on the chain length. Longer is the chain length, lesser is the solubility/boiling point as the extent of H-bonding decreases. Also, the hydrophobic nature of the hydrocarbon chain reduces the solubility.
thus order of solubility and boiling point will be:
$CH _3CH _2OH>CH _3CH _2CH _2OH>CH _3CH _2CH _2CH _2OH$

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Which of the following is not a characteristic of alcohol ?

  1. They are lighter than water.

  2. Their boiling points rise fairly uniformly with rising molecular weight.

  3. Lower members are insoluble in water and organic solvents but the solubility regularly increases with molecular mass.

  4. Lower members have a pleasant smell and burning taste, higher members are colourless and tasteless.

  5. Higher members have a pleasant smell and burning taste, lower members are colourless and tasteless.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
A. Alcohols are lighter than water because water molecules are closely packed together due to extensive H-bonding, which means that it has more mass in the same volume than either alcohol or oil. In addition, alcohol is made up of carbon and hydrogen atoms while water is made up of oxygen and hydrogen atoms.
B. Their boiling points rise fairly uniformly with rising molecular weight this is because boiling point depends on the intermolecular interactions such as H-bonding which decreases as the chain length decreases.
C. Lower members are soluble in water and organic solvents but the solubility regularly decreases with molecular mass because of ease of H-bonding in smaller alcohol molecules than those having long hydrocarbon chain.
D. Lower members have a pleasant smell and burning taste, higher members are colourless and tasteless.
Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Unlike phenol, 2,4-dinitrophenol is soluble in sodium carbonate solution in water because ?

  1. presence of two - $NO _2$ groups in the ring makes 2 , 4 - dinitrophenol a stronger acid than phenol.
  2. presence of two - $NO _2$ groups in the ring makes 2 , 4 - dinitrophenol a weaker acid than phenol.
  3. presence of two $-NO _2$ groups make the hydrogen bonding easier, making 2 , 4-dinitrophenol soluble.
  4. nitro group reacts with $Na _2CO _3$ while -$OH$ group does not.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Presence of two electron withdrawing $-No _2$ groups in the ring makes 2,4-dinitrophenol a stronger acid than phenol. Hence it react with aqueous  $Na _2CO _3$ solution to form sodium salt thus making it soluble in $Na _2CO _3$ . 

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

The compound which gets dissolved in water is :

  1. $C _{2}H _{6}$
  2. $C _{2}H _{4}$
  3. $C _{2}H _{2}$
  4. $C _{2}H _{5}OH$
  5. $C _{3}H _{8}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option D or Ethanol dissolves in water. 


Ethanol has electronegative oxygen atom in it, and hence it takes part in hydrogen bonding with water. 

Because of excessive hydrogen bonding with water, Ethanol dissolves in it.

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Which of the following cannot be dissolved in alcohol?

  1. Dyes and drugs

  2. Soaps and varnishes

  3. Resins and varnishes

  4. Rubber and plastics
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Rubber and plastic cannot be dissloved in alchol because of nonpolar nature of rubber and plastics

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Which of the following has a higher boiling point?

  1. Butanol

  2. Butanal

  3. Both of them have similar boiling point

  4. Cannot say anything

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There is a large difference between boiling points of butanol and butanal, although they have almost the same solubility in water. Butanol contains -OH group and can form hydrogen bonds. Hence, the molecules are associated. A large amount of energy is required to break the association. Hence, butanol has a higher boiling point. Hydrogen bonding is not possible in butanal.

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Solubility of alcohols in water is _______ to that of hydrocarbons of comparable molecular masses.

  1. greater than

  2. similar

  3. lesser than

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Since alcohols can participate in $H-$bonding while hydrocarbons cannot, alcohols are able to interact with water molecules more easily than hydrocarbons of comparable molecular masses. Hence alcohols possess greater solubility in water than hydrocarbons of comparable molecular masses.
Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)
Lower alcohols are more soluble in water than higher alcohols.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lower alcohols are more soluble in water than higher alcohols. With the increase in the molar mass, solubility decreases. In alcohols, $-OH$ group is polar and forms hydrogen bonds with water. This makes alcohol water soluble. The alkyl chain (hydrocarbon chain) is non-polar and decreases the solubility of alcohol in water.

Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

Alcohols containing only up to ________________ carbon atoms are completely miscible with water.

  1. 10

  2. 3

  3. 8

  4. 14
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 Alcohol-containing up to $3-$ carbon atoms are completely miscible with water in all proportions. This is due to the hydrogen bonding with water molecule.