Question

The compound which has the highest freezing point (in K) is

• A. CS$_2$
• B. CHCl$_3$
• C. (C$_2$H$_5$)$_2$O
• D. H$_2$O
• E. C$_2$H$_5$OH

Hint:

Chemistry Tip: Whenever H$_2$O appears in intermolecular-force comparisons, check hydrogen bonding first because it often dominates boiling/freezing point trends.

Answer 1

The Correct Option is D

Concept:
Freezing point depends on how strongly molecules attract each other in the liquid state. Stronger intermolecular forces $\Rightarrow$ molecules arrange into solid form more easily $\Rightarrow$ generally higher freezing point. Main intermolecular forces are:

• London dispersion force
• Dipole-dipole force
• Hydrogen bonding (strongest among these)

Step 1: Analyse each compound.
(A) CS$_2$
It is a non-polar linear molecule. It mainly has weak dispersion forces. (B) CHCl$_3$
Polar molecule. Has dipole-dipole attraction, but no strong hydrogen bonding. (C) (C$_2$H$_5$)$_2$O (diethyl ether)
Slightly polar molecule. Cannot form strong intermolecular hydrogen bonding because it has no O-H bond. (D) H$_2$O
Water molecules form extensive hydrogen bonding network: $$\text{H-O}\cdots\text{H-O}$$ This creates unusually strong attraction between molecules. (E) C$_2$H$_5$OH (ethanol)
Also shows hydrogen bonding, but weaker and less extensive than water because of bulky ethyl group.
Step 2: Compare water and ethanol carefully.
Both water and ethanol hydrogen bond, but:

• Water can form a 3D network of hydrogen bonds.
• Each water molecule can strongly interact with several neighbors.
• Ethanol has one polar OH group but also a non-polar hydrocarbon part.

Therefore water has stronger collective intermolecular attraction.
Step 3: Use actual trend.
Approximate freezing points:

• H$_2$O = $273,K$
• Ethanol $\approx 159,K$
• Others are still lower

So highest freezing point is water.
Step 4: Final answer.
Hence the compound with highest freezing point is: $$\boxed{\text{H}_2\text{O}}$$ Therefore correct option is (D). :contentReference[oaicite:0]{index=0}