Grade 12 Chemistry
For which of the following compounds is hydrogen bonding the main intermolecular force?
Question 19 options:
a) CS2
b) HCN
c) HBr
d) H2
e) H2O2
The correct answer is e) H2O2. Hydrogen bonding is the main intermolecular force in compounds that contain hydrogen atoms bonded to highly electronegative elements such as oxygen (O) or nitrogen (N). In H2O2, hydrogen bonding occurs between the hydrogen atoms and the oxygen atoms in the molecule.
The main intermolecular force for a compound is determined by the presence of hydrogen bonding. In order to determine which compound has hydrogen bonding as the main intermolecular force, we need to assess the polarity of the compound and the presence of hydrogen bound to oxygen, nitrogen, or fluorine.
a) CS2 (carbon disulfide) does not have hydrogen bonding as it does not contain hydrogen atoms bonded to oxygen, nitrogen, or fluorine.
b) HCN (hydrogen cyanide) does not have hydrogen bonding as the hydrogen atom is bonded to carbon and not oxygen, nitrogen, or fluorine.
c) HBr (hydrogen bromide) has hydrogen bonding as the hydrogen atom is bonded to bromine, which is more electronegative than hydrogen. However, its principal intermolecular forces are dipole-dipole interactions due to its polar nature.
d) H2 (hydrogen) does not have hydrogen bonding as it does not contain hydrogen atoms bonded to oxygen, nitrogen, or fluorine. Its main intermolecular forces are London dispersion forces.
e) H2O2 (hydrogen peroxide) has hydrogen bonding as it contains hydrogen atoms bonded to oxygen. Hydrogen bonding is the main intermolecular force in this compound.
Therefore, the compound with hydrogen bonding as the main intermolecular force is e) H2O2 (hydrogen peroxide).
To determine which compound has hydrogen bonding as the main intermolecular force, we need to understand what hydrogen bonding is and what conditions are necessary for it to occur.
Hydrogen bonding is a type of intermolecular force that occurs when a hydrogen atom is bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine) and is attracted to another electronegative atom nearby. This creates a strong dipole-dipole interaction.
Now, let's evaluate each compound:
a) CS2: Carbon disulfide (CS2) does not have hydrogen bonding because it does not contain hydrogen atoms consistently bonded to an electronegative atom. The bonding in CS2 is due to London dispersion forces (also known as van der Waals forces).
b) HCN: Hydrogen cyanide (HCN) has a hydrogen atom bonded to a highly electronegative atom (nitrogen), so it is capable of forming hydrogen bonds. Therefore, HCN can have hydrogen bonding as the main intermolecular force.
c) HBr: Hydrogen bromide (HBr) has a hydrogen atom bonded to a highly electronegative atom (bromine), making it capable of forming hydrogen bonds. Hence, HBr can have hydrogen bonding as the main intermolecular force.
d) H2: Hydrogen gas (H2) consists of diatomic hydrogen molecules. Although the individual H2 molecules are polar due to the difference in electronegativity between the hydrogen atoms, hydrogen bonding does not occur among H2 molecules because each H2 molecule does not have a highly electronegative atom bonded to a hydrogen atom.
e) H2O2: Hydrogen peroxide (H2O2) has two hydrogen atoms bonded to an oxygen atom, which is highly electronegative. It can form hydrogen bonds. Therefore, H2O2 can have hydrogen bonding as the main intermolecular force.
In conclusion, compounds b) HCN, c) HBr, and e) H2O2 can exhibit hydrogen bonding as the main intermolecular force.