Question

question 4 (10 points)
choose the response that lists the member of each of the following pairs that has the higher boiling point.
i. h₂o or ki, ii. hf or hi, iii. cl₂ or br₂
a) ki, hf, and cl₂
b) h₂o, hi, and cl₂
c) ki, hi, and br₂
d) ki, hf, and br₂
e) h₂o, hf, and cl₂

Explanation:

Step1: Analyze Pair I (H₂O or KI)

KI is an ionic compound; ionic compounds have strong ionic bonds. H₂O is molecular with hydrogen bonding. Ionic bonds (in KI) are stronger than H-bonds in H₂O, so KI has a higher boiling point.

Step2: Analyze Pair II (HF or HI)

HF has strong hydrogen bonding (due to F's high electronegativity). HI has only London dispersion forces (LDF), and LDF strength increases with molar mass, but H-bonding in HF is stronger than LDF in HI. So HF has a higher boiling point.

Step3: Analyze Pair III (Cl₂ or Br₂)

Both are nonpolar, so LDF. Molar mass of Br₂ (\(159.8\ g/mol\)) > Cl₂ (\(70.9\ g/mol\)). Higher molar mass means stronger LDF, so Br₂ has a higher boiling point.

Now check options:

• Option D: KI (I), HF (II), Br₂ (III) – matches all three pairs.

Answer:

D. KI, HF, and Br₂