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To determine the types of intermolecular forces acting on each substance, we first need to know the molecular structure and its polarity. a. \(\mathrm{N}_{2}\): Nitrogen is a diatomic molecule consisting of two nitrogen atoms bonded together through a triple bond. Since both atoms have the same electronegativity, there is no polarity in the bond. b. \(\mathrm{NH}_{3}\): Ammonia is a trigonal pyramidal molecule with the nitrogen atom at the apex and the three hydrogen atoms forming the base. The nitrogen-hydrogen bonds are polar due to the difference in electronegativities between nitrogen and hydrogen. c. He: Helium is a noble gas and exists as individual atoms. d. \(\mathrm{CO}_{2}\): Carbon dioxide is a linear molecule with an oxygen atom double-bonded to each side of the carbon atom. Though the individual bonds are polar, the overall molecule is nonpolar due to the symmetry of the molecule.

Now we can identify the types of intermolecular forces in these substances. a. \(\mathrm{N}_{2}\): Since \(\mathrm{N}_{2}\) is a nonpolar molecule, the intermolecular forces present are London dispersion forces. These forces arise due to momentary fluctuations in electron density, forming temporary dipoles that attract neighboring molecules. b. \(\mathrm{NH}_{3}\): In \(\mathrm{NH}_{3}\), there is hydrogen bonding, a type of dipole-dipole force. Hydrogen bonding occurs when a hydrogen atom is covalently bonded to a more electronegative atom like nitrogen, oxygen, or fluorine, creating a strong dipole. The positive end of the dipole (hydrogen) attracts the negative end (lone pair of electrons) on the nitrogen atom of a neighboring molecule, forming a relatively strong intermolecular bond called hydrogen bond. c. He: As helium exists as individual atoms (without any bonds), the only intermolecular forces present are the weak London dispersion forces. d. \(\mathrm{CO}_{2}\): Since \(\mathrm{CO}_{2}\) is a nonpolar molecule, the intermolecular forces present are London dispersion forces, as in the case of \(\mathrm{N}_{2}\). To summarize, the different types of intermolecular forces present in the liquid state of the given substances are: a. \(\mathrm{N}_{2}\): London dispersion forces b. \(\mathrm{NH}_{3}\): Hydrogen bonding c. He: London dispersion forces d. \(\mathrm{CO}_{2}\): London dispersion forces