Question

which substance will have the highest melting point?
c₂h₃cl₃
c₅h₉cl₃
c₃h₅cl₃
c₄h₇cl₃
chcl₃

Explanation:

Step1: Understand the relationship between molar mass and melting point

For similar types of compounds (in this case, these are all chloro - hydrocarbons), as the molar mass increases, the strength of London dispersion forces (a type of van der Waals force) generally increases. Higher molar mass means more electrons and a larger electron cloud, which can lead to stronger instantaneous dipoles and thus stronger intermolecular forces.

Step2: Calculate the molar mass of each compound

• For \(CHCl_3\):

The molar mass \(M(CHCl_3)=(12 + 1+3\times35.5)\space g/mol=(13 + 106.5)\space g/mol = 119.5\space g/mol\)

• For \(C_2H_3Cl_3\):

\(M(C_2H_3Cl_3)=(2\times12 + 3\times1+3\times35.5)\space g/mol=(24 + 3+106.5)\space g/mol=133.5\space g/mol\)

• For \(C_3H_5Cl_3\):

\(M(C_3H_5Cl_3)=(3\times12 + 5\times1+3\times35.5)\space g/mol=(36+5 + 106.5)\space g/mol=147.5\space g/mol\)

• For \(C_4H_7Cl_3\):

\(M(C_4H_7Cl_3)=(4\times12 + 7\times1+3\times35.5)\space g/mol=(48+7+106.5)\space g/mol=161.5\space g/mol\)

• For \(C_5H_9Cl_3\):

\(M(C_5H_9Cl_3)=(5\times12 + 9\times1+3\times35.5)\space g/mol=(60 + 9+106.5)\space g/mol=175.5\space g/mol\)

Answer:

\(C_5H_9Cl_3\)