Which of the following molecules does not have a dipole moment?
1) CBr2=CBr2
2) NCl3
3) CH3NH2
4) HCl
Which of the following exhibits ion-dipole forces?
1) KBr(s)
2) NaF(aq)
3) Ag(s)
4) Cl2(g)
H
To determine whether a molecule has a dipole moment, we need to consider its molecular shape and the polarity of its bonds. A dipole moment occurs when there is an uneven distribution of charge in a molecule, causing one end to be partially positive and the other end to be partially negative.
1) CBr2=CBr2: This molecule is linear and symmetrical, meaning it has no overall dipole moment.
2) NCl3: Nitrogen trichloride has a trigonal pyramidal shape, with the nitrogen atom as the central atom and three chlorine atoms arranged around it. The chlorine atoms have a higher electronegativity than nitrogen, creating a polar molecule with a dipole moment.
3) CH3NH2: Methylamine has a pyramidal shape, with the nitrogen atom as the central atom bonded to three hydrogen atoms and one methyl group. The nitrogen and hydrogen atoms have different electronegativities, resulting in a polar molecule with a dipole moment.
4) HCl: Hydrogen chloride has a linear shape, with hydrogen and chlorine atoms bonded together. Chlorine is more electronegative than hydrogen, causing the molecule to have a polar covalent bond and a dipole moment.
From the given options, the molecule that does not have a dipole moment is 1) CBr2=CBr2.
To determine whether a molecule has a dipole moment, you need to consider the individual bond polarities and the overall molecular geometry. A dipole moment occurs when there is a separation of charge within a molecule leading to a positive and negative end. If the molecule has a symmetrical shape or has bond polarities that cancel each other out, then it does not have a dipole moment.
Let's analyze each of the given molecules:
1) CBr2=CBr2: This molecule is symmetrical, meaning that the chlorine atoms (electronegativity: 3.16) on either side of the central carbon atom (electronegativity: 2.55) are in an equal and opposite arrangement. Therefore, the bond polarities cancel each other out, resulting in a nonpolar molecule. Thus, this molecule does not have a dipole moment.
2) NCl3: Nitrogen (electronegativity: 3.04) and chlorine (electronegativity: 3.16) have a difference in electronegativity, indicating that the N-Cl bonds are polar. However, the molecule's molecular geometry is pyramidal, leading to an imbalance in polarity. As a result, NCl3 is a polar molecule and has a dipole moment.
3) CH3NH2: Carbon (electronegativity: 2.55) and hydrogen (electronegativity: 2.20) have little electronegativity difference, so their C-H bonds are considered nonpolar. The nitrogen atom (electronegativity: 3.04) and the hydrogen atoms create a tetrahedral geometry. The polarities of the N-H bonds do not cancel each other out, resulting in a polar molecule with a dipole moment.
4) HCl: Hydrogen (electronegativity: 2.20) and chlorine (electronegativity: 3.16) have a significant electronegativity difference. As a result, the H-Cl bond is polar. Additionally, the molecule's linear geometry prevents any cancellation of bond polarities. Therefore, HCl is a polar molecule with a dipole moment.
To summarize, the molecule without a dipole moment is option 1) CBr2=CBr2.