Question

Indicate whether each of the statements below is true or false. 1. CBr4 is more volatile than CCl4. 2. CBr4 has a higher vapor pressure at the same temperature than CCl4. 3. CBr4 has a higher boiling point than CCl4. 4. CBr4 has weaker intermolecular forces than CCl4.

Answer 1

Answer:

1. False

2. False

3. True

4. False

Explanation:

1. CBr4 is more volatile than CCl4  False

The molecular weight of CBr4 is is greater than the CCl4,  therefore it has less tendency to escape to the gas phase. Also, the CBr4 has greater London dispersion forces compared to CCl4 since bromine is a larger atom than chlorine.

2. CBr4 has a higher vapor pressure at the same temperature than CCl4 False

For the same reasons as above,  the vapor pressure of CBr4 is smaller than the vapor pressure of CCl4

3. CBr4 has a higher boling point than CCl4 True

Again, CBr4 having a molecular weight greater than CCl4  ( 331  g/mol vs 158.2 g/mol) is heavier and less volatile with a higher boiling point than CCl4.

4. CBr4 has weaker intermolecular forces than CCl4 False

Both molecules are non-polar because the dipole moments in C-Cl and C-Br bonds cancel in the tetrahedron. The only possible molecular forces are of the London dispersion  type which are temporary  and greater for larger atoms.