Answer:
Dipole-dipole attractions
Explanation:
PBr₃ is a <em>trigonal pyramidal</em> molecule.
The P-Br bonds are polar, with their bond dipoles pointing toward the Br atoms (see below).
The x-components of the dipoles cancel, but the y-components reinforce each other.
The partially negative Br atoms are attracted to the partially positive N atoms in neighboring molecules.
These dipole-dipole forces are the strongest intermolecular forces in PBr₃.
Answer:
w = -531 kJ
1. Work was done by the system.
Explanation:
Step 1: Given data
- Heat gained by the system (q): 687 kJ (By convention, when the system absorbs heat, q > 0).
- Change in the internal energy of the system (ΔU°): 156 kJ
Step 2: Calculate the work done (w)
We will use the following expression.
ΔU° = q + w
w = ΔU° - q
w = 156 kJ - 687 kJ
w = -531 kJ
By convention, when w < 0, work is done by the system on the surroundings.