Final answer:
Placing HBr under very high pressure that decreases its bond length, while assuming constant effective charges, would result in an increased dipole moment.
Step-by-step explanation:
The question revolves around the concept of a dipole moment and how it may be affected by changes in bond length under high pressure, as in the case of hydrogen bromide (HBr). The dipole moment of a molecule is a measure of the separation of positive and negative charge. It is calculated by multiplying the amount of charge separated by the distance over which it is separated, which is essentially the bond length.
If we place HBr under very high pressure, causing the bond length to decrease while assuming that the effective charges on the atoms do not change, the dipole moment would increase. This is because the dipole moment formula (dipole moment = charge × distance) would have a smaller denominator (distance), leading to a larger result when the numerator (charge) remains constant.
It is also important to understand that dipole-dipole interactions are related to the dipole moments of the molecules. An increased dipole moment would typically mean stronger dipole-dipole interactions, potentially affecting boiling points and other physical properties of the compound when in a liquid or solid state. However, one must also be aware that drastic changes in pressure could lead to changes in intermolecular forces as well, adding to the complexity of predicting physical properties under such conditions.